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CATH Superfamily 3.10.120.10

Cytochrome b5-like heme/steroid binding domain

The name of this superfamily has been modified since the most recent official CATH+ release (v4_3_0). At the point of the last release, this superfamily was named:

"
Cytochrome b5-like heme/steroid binding domain
".

Functional Families

Overview of the Structural Clusters (SC) and Functional Families within this CATH Superfamily. Clusters with a representative structure are represented by a filled circle.

Superfamily EC Annotations

Note: the EC figure is not being displayed for this superfamily as there are more than 100 different EC terms.

There are 23 EC terms in this cluster

Please note: EC annotations are assigned to the full protein sequence rather than individual protein domains. Since a given protein can contain multiple domains, it is possible that some of the annotations below come from additional domains that occur in the same protein, but have been classified elsewhere in CATH.

Note: The search results have been sorted with the annotations that are found most frequently at the top of the list. The results can be filtered by typing text into the search box at the top of the table.

EC Term Annotations Evidence
Nitrate reductase (NADH). [EC: 1.7.1.1]
Nitrite + NAD(+) + H(2)O = nitrate + NADH.
  • Formerly EC 1.6.6.1.
 29 A0A125YVC5 A0A178WBR8 A0A1S3ZD90 A0A1U7UPF8 P08509 P11035 P11605 P11832 P16081 P17569
(19 more...)
Acyl-CoA 6-desaturase. [EC: 1.14.19.3]
(1) Linoleoyl-CoA + 2 ferrocytochrome b5 + O(2) + 2 H(+) = gamma- linolenoyl-CoA + 2 ferricytochrome b5 + 2 H(2)O. (2) Alpha-linolenoyl-CoA + 2 ferrocytochrome b5 + O(2) + 2 H(+) = stearidonoyl-CoA + 2 ferricytochrome b5 + 2 H(2)O.
  • The enzyme introduces a cis double bond at carbon 6 of acyl-CoAs.
  • It is a front-end desaturase, introducing the new double bond between a pre-existing double bond and the carboxyl-end of the fatty acid.
  • The human enzyme has a broad substrate range; it also acts on palmitoyl-CoA, generating sapienoyl-CoA, and on (9Z,12Z,15Z,18Z,21Z)- tetracosa-9,12,15,18,21-pentaenoyl-CoA, converting it to (6Z,9Z,12Z,15Z,18Z,21Z)-tetracosa-6,9,12,15,18,21-hexaenoyl-CoA as part of a pathway that produces docosahexaenoate.
  • The enzyme contains a cytochrome b5 domain that is assumed to act in vivo as the electron donor to the active site of the desaturase.
 17 A0A0C5PRW9 A0A0D9R2C8 A0A2J8SMN3 A0A2K5NWS9 A0A2K6D4T4 A0A2R9BKZ6 A4FV48 B8R1K0 F6YUF6 G7PPX1
(7 more...)
Nitrate reductase (NADPH). [EC: 1.7.1.3]
Nitrite + NADP(+) + H(2)O = nitrate + NADPH.
  • Formerly EC 1.6.6.3.
 10 P08619 P22945 P36842 P36858 P39863 P39864 P43100 P49050 Q05531 Q7LLV6
L-lactate dehydrogenase (cytochrome). [EC: 1.1.2.3]
(S)-lactate + 2 ferricytochrome c = pyruvate + 2 ferrocytochrome c + 2 H(+).
    		 10 A0A0L8VKD8 A6ZM12 B3LLK2 C7GME9 C8ZEF3 G2WK02 H0GLT0 N1NZC2 P00175 P09437
    Dihydroceramide fatty acyl 2-hydroxylase. [EC: 1.14.18.7]
    A dihydroceramide + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (2'R)- 2'-hydroxydihydroceramide + 2 ferricytochrome b5 + H(2)O.
    • The enzyme, characterized from plants, catalyzes the hydroxylation of carbon 2 of long- or very-long-chain fatty acids attached to sphinganine during de novo ceramide synthesis.
    • The enzyme requires an external cytochrome b5 as the electron donor.
    • The newly introduced 2-hydroxyl group has R-configuration.
    • Cf. EC 1.14.18.6.
    		 9 A0A0L8VJ82 A6ZMY7 B3LMF9 C7GTM8 C8ZFD7 G2WKY0 H0GLG7 N1NXQ7 Q03529
    4-hydroxysphinganine ceramide fatty acyl 2-hydroxylase. [EC: 1.14.18.6]
    A phytoceramide + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (2'R)- 2'-hydroxyphytoceramide + 2 ferricytochrome b5 + H(2)O.
    • The enzyme, characterized from yeast and mammals, catalyzes the hydroxylation of carbon 2 of long- or very-long-chain fatty acids attached to (4R)-4-hydroxysphinganine during de novo ceramide synthesis.
    • The enzymes from yeast and from mammals contain an N-terminal cytochrome b5 domain that acts as the direct electron donor to the desaturase active site.
    • The newly introduced 2-hydroxyl group has R-configuration.
    • Cf. EC 1.14.18.7.
    		 9 A0A0L8VJ82 A6ZMY7 B3LMF9 C7GTM8 C8ZFD7 G2WKY0 H0GLG7 N1NXQ7 Q03529
    Cytochrome-b5 reductase. [EC: 1.6.2.2]
    NADH + 2 ferricytochrome b5 = NAD(+) + H(+) + 2 ferrocytochrome b5.
      		 8 A0A2R9CF58 H2QTC4 Q28CZ9 Q32LH7 Q3TDX8 Q502I6 Q68EJ0 Q7L1T6
      Sulfite oxidase. [EC: 1.8.3.1]
      Sulfite + O(2) + H(2)O = sulfate + H(2)O(2).
        		 7 A0A024RB79 P07850 P51687 Q07116 Q60HD0 Q8R086 Q9VWP4
        Acyl-CoA (8-3)-desaturase. [EC: 1.14.19.44]
        (1) (8Z,11Z,14Z)-icosa-8,11,14-trienoyl-CoA + 2 ferrocytochrome b5 + O(2) + 2 H(+) = arachidonoyl-CoA + 2 ferricytochrome b5 + 2 H(2)O. (2) (8Z,11Z,14Z,17Z)-icosa-8,11,14,17-tetraenoyl-CoA + 2 ferrocytochrome b5 + O(2) + 2 H(+) = (5Z,8Z,11Z,14Z,17Z)-icosa-5,8,11,14,17-pentaenoyl- CoA + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme introduces a cis double bond at carbon 5 of acyl-CoAs that contain a double bond at position 8.
        • The enzymes from algae, mosses, mammals and the protozoan Leishmania major catalyze the desaturation of dihomo-gamma-linoleate ((8Z,11Z,14Z)-icosa-8,11,14-trienoate) and (8Z,11Z,14Z,17Z)-icosa- 8,11,14,17-tetraenoate to generate arachidonate and (5Z,8Z,11Z,14Z,17Z)-icosa-5,8,11,14,17-pentaenoate, respectively.
        • The enzyme contains a cytochrome b5 domain that acts as the direct electron donor to the desaturase active site and does not require an external cytochrome.
        • Cf. EC 1.14.19.37.
        		 6 A0A2J8LDB7 A4UVI1 O60427 Q920L1 Q920R3 X2EXD0
        Sphingolipid 8-(E)-desaturase. [EC: 1.14.19.18]
        A (4E)-sphing-4-enine ceramide + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (4E,8E)-sphing-4,8-dienine ceramide + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme, characterized from the yeasts Kluyveromyces lactis and Candida albicans and from the diatom Thalassiosira pseudonana, introduces a trans double bond at the 8-position of sphingoid bases in sphingolipids.
        • The enzyme determines the position of the double bond by its distance from the alcohol end of the sphingoid base, and contains a cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase.
        • The homologous enzymes from higher plants, EC 1.14.19.29, act on phytosphinganine (4-hydroxysphinganine) and produces a mixture of trans and cis isomers.
        		 6 C4QVU3 F2QNN3 Q5AEK8 Q6CMK7 Q8NKG8 Q8NKG9
        Acyl-lipid (8-3)-desaturase. [EC: 1.14.19.30]
        (1) An (8Z,11Z,14Z)-icosa-8,11,14-trienoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (5Z,8Z,11Z,14Z)-icosatetra- 5,8,11,14-tetraenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O. (2) An (8Z,11Z,14Z,17Z)-icosa-8,11,14,17-tetraenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (5Z,8Z,11Z,14Z,17Z)-icosa- 5,8,11,14,17-pentaenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme, which has been characterized from multiple organisms including the moss Physcomitrella patens, the marine microalga Rebecca salina, and the filamentous fungus Mortierella alpina, introduces a cis double bond at the 5-position in 20-carbon polyunsaturated fatty acids incorporated in a glycerolipid that contain a Delta(8) double bond.
        • The enzyme contains a cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase, and does not require an external cytochrome.
        		 6 A0A2K1JC31 A4KDP0 A9SIZ6 O74212 O96099 Q8S3C1
        Sphingolipid 8-(E/Z)-desaturase. [EC: 1.14.19.29]
        (1) A (4R)-4-hydroxysphinganine ceramide + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (4R,8E)-4-hydroxysphing-8-enine ceramide + 2 ferricytochrome b5 + 2 H(2)O. (2) A (4R)-4-hydroxysphinganine ceramide + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (4R,8Z)-4-hydroxysphing-8-enine ceramide + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzymes from higher plants convert sphinganine, 4E-sphing-4-enine and phytosphinganine into E/Z-mixtures of Delta(8)-desaturated products displaying different proportions of geometrical isomers depending on plant species.
        • The nature of the actual desaturase substrate has not yet been studied experimentally.
        • The enzymes contain an N-terminal cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase.
        • The homologous enzymes from some yeasts and diatoms, EC 1.14.19.18, act on sphing-4-enine ceramides and produce only the trans isomer.
        		 6 A0A178V7U9 A0A251S2B6 Q3EBF7 Q43469 Q9FR82 Q9ZRP7
        Acyl-lipid (7-3)-desaturase. [EC: 1.14.19.31]
        (1) A (7Z,10Z,13Z,16Z,19Z)-docosa-7,10,13,16,19-pentaenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (4Z,7Z,10Z,13Z,16Z,19Z)- docosa-4,7,10,13,16,19-hexaenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O. (2) A (7Z,10Z,13Z,16Z)-docosa-7,10,13,16-tetraenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (4Z,7Z,10Z,13Z,16Z)-docosa- 4,7,10,13,16-pentaenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzymes from several algae introduce a cis double bond at the 4-position in 22-carbon polyunsaturated fatty acids that contain a Delta(7) double bond.
        • The enzyme from the fresh water alga Chlamydomonas reinhardtii acts on the 16 carbon fatty acid (7Z,10Z,13Z)-hexadeca-7,10,13-trienoate.
        • The enzyme contains an N-terminal cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase, and does not require an external cytochrome.
        		 6 A0A2K3E764 A0PJ29 I2CYZ4 Q6VPV2 Q6WNG7 Q8S3C0
        Stearoyl-CoA 9-desaturase. [EC: 1.14.19.1]
        Stearoyl-CoA + 2 ferrocytochrome b5 + O(2) + 2 H(+) = oleoyl-CoA + 2 ferricytochrome b5 + 2 H(2)O.
        • The liver enzyme is an enzyme system involving cytochrome b5 and EC 1.6.2.2.
        • The ferricytochrome b5 produced is reduced by NADH and EC 1.6.2.2.
        • Formerly EC 1.14.99.5.
        		 4 N1P3L6 O94523 P21147 Q12618
        Acyl-lipid (9-3)-desaturase. [EC: 1.14.19.47]
        (1) An alpha-linolenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a stearidonoyl-[glycerolipid] + ferricytochrome b5 + 2 H(2)O. (2) A linoleoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a gamma-linolenoyl-[glycerolipid] + ferricytochrome b5 + 2 H(2)O.
        • The enzyme, characterized from the moss Physcomitrella patens and the plant Borago officinalis (borage), introduces a cis double bond at carbon 6 of several acyl-lipids that contain an existing Delta(9) cis double bond.
        • The enzyme contains a cytochrome b5 domain that acts as the electron donor for the active site of the desaturase.
        		 4 O04353 Q9LEM9 Q9LEN0 Q9ZNW2
        Acyl-lipid omega-(9-4) desaturase. [EC: 1.14.19.12]
        (1) Linoleoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = pinolenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O. (2) Alpha-linolenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = coniferonoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme, characterized from the green alga Chlamydomonas reinhardtii, is a front-end desaturase that introduces a cis double bond in omega(9) unsaturated C(18) or C(20) fatty acids incorporated into lipids, at a position 4 carbon atoms from the existing omega(9) bond, toward the carboxy end of the fatty acid (at the omega(13) position).
        • When acting on 20:2-Delta-(11,14) and 20:3-Delta-(11,14,17) substrates it introduces the new double bond between carbons 7 and 8.
        • The enzyme contains a cytochrome b5 domain that acts as the direct electron donor for the active site of the desaturase.
        		 2 A0A2K3DBB8 Q2HWK7
        HECT-type E3 ubiquitin transferase. [EC: 2.3.2.26]
        S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)- ubiquitinyl-[acceptor protein]-L-lysine.
        • In the first step the enzyme transfers ubiquitin from the E2 ubiquitin-conjugating enzyme (EC 2.3.2.23) to a cysteine residue in its HECT domain (which is located in the C-terminal region), forming a thioester bond.
        • In a subsequent step the enzyme transfers the ubiquitin to an acceptor protein, resulting in the formation of an isopeptide bond between the C-terminal glycine residue of ubiquitin and the epsilon- amino group of an L-lysine residue of the acceptor protein.
        • Cf. EC 2.3.2.27 and EC 2.3.2.31.
        		 2 O95714 Q4U2R1
        Nitrate reductase (NAD(P)H). [EC: 1.7.1.2]
        Nitrite + NAD(P)(+) + H(2)O = nitrate + NAD(P)H.
        • Formerly EC 1.6.6.2.
        		 2 P27783 P27968
        Chitin synthase. [EC: 2.4.1.16]
        UDP-N-acetyl-alpha-D-glucosamine + (1,4-(N-acetyl-beta-D- glucosaminyl))(n) = UDP + (1,4-(N-acetyl-beta-D-glucosaminyl))(n+1).
        • Converts UDP-N-acetyl-D-glucosamine into chitin and UDP.
        		 1 O13395
        (S)-mandelate dehydrogenase. [EC: 1.1.99.31]
        (S)-2-hydroxy-2-phenylacetate + acceptor = 2-oxo-2-phenylacetate + reduced acceptor.
        • While all enzymes of this family oxidize the (S)-enantiomer of an alpha-hydroxy acid to an alpha-oxo acid, the ultimate oxidant (oxygen, intramolecular heme or some other acceptor) depends on the particular enzyme.
        • Transfers the electron pair from FMNH(2) to a component of the electron transport chain, most probably ubiquinone.
        • It is part of a metabolic pathway in Pseudomonads that allows these organisms to utilize mandelic acid, derivatized from the common soil metabolite amygdalin, as the sole source of carbon and energy.
        • Has a large active-site pocket and preferentially binds substrates with longer sidechains, e.g. 2-hydroxyoctanoate rather than 2-hydroxybutyrate.
        • It also prefers substrates that, like (S)-mandelate, have beta unsaturation, e.g. (indol-3-yl)glycolate compared with (indol-3- yl)lactate.
        • Esters of mandelate, such as methyl (S)-mandelate, are also substrates.
        		 1 P32953
        Acyl-lipid (11-3)-desaturase. [EC: 1.14.19.4]
        (1) An (11Z,14Z)-icosa-11,14-dienoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = an (8Z,11Z,14Z)-icosa-8,11,14-trienoyl- [glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O. (2) An (11Z,14Z,17Z)-icosa-11,14,17-trienoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = an (8Z,11Z,14Z,17Z)-icosa- 8,11,14,17-tetraenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme, characterized from the protist Euglena gracilis and the microalga Rebecca salina, introduces a cis double bond at the 8-position in 20-carbon fatty acids that are incorporated into a glycerolipid and have an existing Delta(11) desaturation.
        • The enzyme is a front-end desaturase, introducing the new double bond between the pre-existing double bond and the carboxyl-end of the fatty acid.
        • It contains a cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase, and does not require an external cytochrome.
        • Involved in alternative pathways for the biosynthesis of the polyunsaturated fatty acids arachidonate and icosapentaenoate.
        		 1 Q9SWQ9
        Acyl-lipid Delta(6)-acetylenase. [EC: 1.14.19.38]
        (1) A gamma-linolenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (9Z,12Z)-octadeca-9,12-dien-6-ynoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O. (2) A stearidonoyl-[glycerolipid] + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (9Z,12Z,15Z)-octadeca-9,12,15-trien-6-ynoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme, characterized from the moss Ceratodon purpureus, converts the double bond at position 6 of gamma-linolenate and stearidonate into a triple bond.
        • The product of the latter, dicranin, is the main fatty acid found in C.purpureus.
        • The enzyme contains a cytochrome b5 domain that acts as the direct electron donor to the desaturase active site.
        • The enzyme also has the activity of EC 1.14.19.47.
        		 1 Q9LEN0
        Sphingolipid 10-desaturase. [EC: 1.14.19.19]
        A (4E,8E)-sphinga-4,8-dienine ceramide + 2 ferrocytochrome b5 + O(2) + 2 H(+) = a (4E,8E,10E)-sphinga-4,8,10-trienine ceramide + 2 ferricytochrome b5 + 2 H(2)O.
        • The enzyme, characterized from the marine diatom Thalassiosira pseudonana, produces an all-trans product.
        • Similar triunsaturated sphingoid bases are found in some marine invertebrates.
        • The enzyme determines the position of the double bond by its distance from the alcohol end of the sphingoid base, and contains a cytochrome b5 domain that acts as the direct electron donor to the active site of the desaturase.
        		 1 Q4G2T3