Enzyme Nomenclature

Continued from EC 5.1.3 and EC 5.1.99

EC 5.2



EC maleate isomerase
EC maleylacetoacetate isomerase
EC deleted covered by EC, EC, EC, and EC
EC maleylpyruvate isomerase
EC linoleate isomerase
EC furylfuramide isomerase
EC transferred now EC
EC peptidylprolyl isomerase
EC farnesol 2-isomerase
EC 2-chloro-4-carboxymethylenebut-2-en-1,4-olide isomerase
EC deleted entry
EC ζ-carotene isomerase
EC prolycopene isomerase
EC β-carotene isomerase



Accepted name: maleate isomerase

Reaction: maleate = fumarate

Systematic name: maleate cis-trans-isomerase

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9023-74-9


1. Behrman, E.J. and Stanier, R.Y. The bacterial oxidation of nicotinic acid. J. Biol. Chem. 228 (1957) 923-945.

[EC created 1961]


Accepted name: maleylacetoacetate isomerase

Reaction: 4-maleylacetoacetate = 4-fumarylacetoacetate

For diagram of reaction click here.

Other name(s): maleylacetoacetic isomerase; maleylacetone isomerase; maleylacetone cis-trans-isomerase

Systematic name: 4-maleylacetoacetate cis-trans-isomerase

Comments: Also acts on maleylpyruvate.

Links to other databases: BRENDA, EAWAG-BBD, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9023-75-0


1. Edwards, S.W. and Knox, W.E. Homogentisate metabolism: the isomerization of methylacetoacetate by an enzyme which requires glutathione. J. Biol. Chem. 220 (1956) 79-91.

2. Lack, L. Enzymic cis-trans isomerization of maleylpyruvic acid. J. Biol. Chem. 236 (1961) 2835-2840.

3. Seltzer, S. Purification and properties of maleylacetone cis-trans isomerase from Vibrio 01. J. Biol. Chem. 248 (1973) 215-222. [PMID: 4692831]

[EC created 1961]

[EC Deleted entry: retinal isomerase. Now known to be catalysed by a pathway involving EC, NADP-retinol dehydrogenase; EC, phosphatidylcholine—retinol O-acyltransferase; EC, retinoid isomerohydrolase; and EC, 11-cis-retinol dehydrogenase. (EC created 1961, modified 1976, deleted 2011)]


Accepted name: maleylpyruvate isomerase

Reaction: 3-maleylpyruvate = 3-fumarylpyruvate

Systematic name: 3-maleylpyruvate cis-trans-isomerase

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 9023-77-2


1. Lack, L. Enzymic cis-trans isomerization of maleylpyruvic acid. J. Biol. Chem. 236 (1961) 2835-2840.

[EC created 1965]


Accepted name: linoleate isomerase

Reaction: 9-cis,12-cis-octadecadienoate = 9-cis,11-trans-octadecadienoate

Other name(s): linoleic acid isomerase

Systematic name: linoleate Δ12-cis-Δ11-trans-isomerase

Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, CAS registry number: 37318-41-5


1. Kepler, C.R. and Tove, S.B. Biohydrogenation of unsaturated fatty acids. III. Purification and properties of linoleate Δ12-cis, Δ11-trans-isomerase from Butyrivibrio fibrosolvens. J. Biol. Chem. 242 (1967) 5686-5692.

[EC created 1972]


Accepted name: furylfuramide isomerase

Reaction: (E)-2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide = (Z)-2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide

Systematic name: 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide cis-trans-isomerase

Comments: Requires NADH.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 72561-07-0


1. Tomoeda, M. and Kitamura, R. A cis-trans isomerising activity of Escherichia coli. Isomerization from 2-(2-furyl)-3-cis-(5-nitro-2-furyl) acrylamide (furylfuramide) to its trans isomer. Biochim. Biophys. Acta 480 (1977) 315-325. [PMID: 12827]

[EC created 1978]

[EC Transferred entry: retinol isomerase. Transferred to EC, retinoid isomerohydrolase. (EC created 1989, deleted 2011)]


Accepted name: peptidylprolyl isomerase

Reaction: peptidylproline (ω=180) = peptidylproline (ω=0)

Glossary: For definition of ω, click here

Other name(s): PPIase; cyclophilin [misleading, see comments]; peptide bond isomerase; peptidyl-prolyl cis-trans isomerase

Systematic name: peptidylproline cis-trans-isomerase

Comments: The first type of this enzyme found [1] proved to be the protein cyclophilin, which binds the immunosuppressant cyclosporin A. Other distinct families of the enzyme exist, one being FK-506 binding proteins (FKBP) and another that includes parvulin from Escherichia coli. The three families are structurally unrelated and can be distinguished by being inhibited by cyclosporin A, FK-506 and 5-hydroxy-1,4-naphthoquinone, respectively.

Links to other databases: BRENDA, EXPASY, KEGG, PDB, Metacyc, CAS registry number: 95076-93-0


1. Fischer, G. and Bang, H. The refolding of urea-denatured ribonuclease A is catalyzed by peptidyl-prolyl cis-trans isomerase. Biochim. Biophys. Acta 828 (1985) 39-42. [PMID: 3882150]

2. Fischer, G., Bang, H. and Mech, C. [Determination of enzymatic catalysis for the cis-trans-isomerization of peptide binding in proline-containing peptides]. Biomed. Biochim. Acta 43 (1984) 1101-1111. [PMID: 6395866]

3. Fischer, G., Wittmann-Liebold, B., Lang, K., Kiefhaber, T. and Schmid, F.X. Cyclophilin and peptidyl-prolyl cis-trans isomerase are probably identical proteins. Nature 337 (1989) 476-478. [PMID: 2492638]

4. Takahashi, N., Hayano, T. and Suzuki, M. Peptidyl-prolyl cis-trans isomerase is the cyclosporin A-binding protein cyclophilin. Nature 337 (1989) 473-475. [PMID: 2644542]

5. Hennig, L., Christner, C., Kipping, M., Schelbert, B., Rucknagel, K.P., Grabley, S., Kullertz, G. and Fischer, G. Selective inactivation of parvulin-like peptidyl-prolyl cis/trans isomerases by juglone. Biochemistry 37 (1998) 5953-5960. [PMID: 9558330]

6. Fischer, G. Peptidyl-prolyl cis/trans isomerases and their effectors. Angew. Chem. Int. Ed. Engl. 33 (1994) 1415-1436.

7. Harrison, R.K. and Stein, R.L. Substrate specificities of the peptidyl prolyl cis-trans isomerase activities of cyclophilin and FK-506 binding protein: evidence for the existence of a family of distinct enzymes. Biochemistry 29 (1990) 3813-3816. [PMID: 1693856]

8. Eisenmesser, E.Z., Bosco, D.A., Akke, M. and Kern, D. Enzyme dynamics during catalysis. Science 295 (2002) 1520-1523. [PMID: 11859194 ]

[EC created 1989, modified 2002]


Accepted name: farnesol 2-isomerase

Reaction: 2-trans,6-trans-farnesol = 2-cis,6-trans-farnesol

For reaction pathway click here.

Other name(s): farnesol isomerase

Systematic name: 2-trans,6-trans-farnesol 2-cis-trans-isomerase

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 94047-16-2


1. Anastasis, P., Freer, I., Gilmore, C., Mackie, H., Overton, K., Picken, D. and Swanson, S. Biosynthesis of γ-bisabolene in tissue-cultures of Andrographis paniculata. Can. J. Chem. 62 (1984) 2079-2088.

[EC created 1989]


Accepted name: 2-chloro-4-carboxymethylenebut-2-en-1,4-olide isomerase

Reaction: cis-2-chloro-4-carboxymethylenebut-2-en-1,4-olide = trans-2-chloro-4-carboxymethylenebut-2-en-1,4-olide

Other name(s): 2-chlorocarboxymethylenebutenolide isomerase; chlorodienelactone isomerase

Systematic name: 2-chloro-4-carboxymethylenebut-2-en-1,4-olide cis-trans-isomerase

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 115629-29-3


1. Schwien, U., Schmidt, E., Knackmuss, H.-J. and Reinecke, W. Degradation of chlorosubstituted aromatic-compounds by Pseudomonas sp. strain-B13 - fate of 3,5-dichlorocatechol. Arch. Microbiol. 150 (1988) 78-84.

[EC created 1992]

[EC Deleted entry: 4-hydroxyphenylacetaldehyde-oxime isomerase. The existence of this enzyme has been called into question by one of the authors of the reference cited (EC created 1992, deleted 2005)]


Accepted name: ζ-carotene isomerase

Reaction: 9,15,9'-tricis-ζ-carotene = 9,9'-dicis-ζ-carotene

For diagram of reaction click here.

Other name(s): Z-ISO; 15-cis-ζ-carotene isomerase

Systematic name: 9,15,9'-tricis-ζ-carotene cis-trans-isomerase

Comments: The enzyme catalyses the cis-trans isomerization of the 15-15' carbon-carbon double bond in 9,15,9'-tricis-ζ-carotene, which is required for biosynthesis of all plant carotenoids. Requires heme b.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Chen, Y., Li, F. and Wurtzel, E.T. Isolation and characterization of the Z-ISO gene encoding a missing component of carotenoid biosynthesis in plants. Plant Physiol. 153 (2010) 66-79. [PMID: 20335404]

2. Li, F., Murillo, C. and Wurtzel, E.T. Maize Y9 encodes a product essential for 15-cis-ζ-carotene isomerization. Plant Physiol. 144 (2007) 1181-1189. [PMID: 17434985]

3. Beltran, J., Kloss, B., Hosler, J.P., Geng, J., Liu, A., Modi, A., Dawson, J.H., Sono, M., Shumskaya, M., Ampomah-Dwamena, C., Love, J.D. and Wurtzel, E.T. Control of carotenoid biosynthesis through a heme-based cis-trans isomerase. Nat. Chem. Biol. 11 (2015) 598-605. [PMID: 26075523]

[EC created 2011]


Accepted name: prolycopene isomerase

Reaction: 7,9,7',9'-tetracis-lycopene = all-trans-lycopene

For diagram of reaction click here.

Glossary: prolycopene = 7,9,7',9'-tetracis-lycopene

Other name(s): CRTISO; carotene cis-trans isomerase; ZEBRA2 (gene name); carotene isomerase; carotenoid isomerase

Systematic name: 7,9,7',9'-tetracis-lycopene cis-trans-isomerase

Comments: Requires FADH2 [1]. The enzyme is involved in carotenoid biosynthesis.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Yu, Q., Ghisla, S., Hirschberg, J., Mann, V. and Beyer, P. Plant carotene cis-trans isomerase CRTISO: a new member of the FADred-dependent flavoproteins catalyzing non-redox reactions. J. Biol. Chem. 286 (2011) 8666-8676. [PMID: 21209101]

2. Li, Q., Farre, G., Naqvi, S., Breitenbach, J., Sanahuja, G., Bai, C., Sandmann, G., Capell, T., Christou, P. and Zhu, C. Cloning and functional characterization of the maize carotenoid isomerase and β-carotene hydroxylase genes and their regulation during endosperm maturation. Transgenic Res. 19 (2010) 1053-1068. [PMID: 20221689]

3. Isaacson, T., Ronen, G., Zamir, D. and Hirschberg, J. Cloning of tangerine from tomato reveals a carotenoid isomerase essential for the production of β-carotene and xanthophylls in plants. Plant Cell 14 (2002) 333-342. [PMID: 11884678]

4. Chai, C., Fang, J., Liu, Y., Tong, H., Gong, Y., Wang, Y., Liu, M., Wang, Y., Qian, Q., Cheng, Z. and Chu, C. ZEBRA2, encoding a carotenoid isomerase, is involved in photoprotection in rice. Plant Mol. Biol. 75 (2011) 211-221. [PMID: 21161331]

[EC created 2011]


Accepted name: β-carotene isomerase

Reaction: all-trans-β-carotene = 9-cis-β-carotene

For diagram of reaction click here.

Other name(s): DWARF27 (gene name)

Systematic name: β-carotene 9-cis-all-trans isomerase

Comments: The enzyme participates in a pathway leading to biosynthesis of strigolactones, plant hormones involved in promotion of symbiotic associations known as arbuscular mycorrhiza.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Lin, H., Wang, R., Qian, Q., Yan, M., Meng, X., Fu, Z., Yan, C., Jiang, B., Su, Z., Li, J. and Wang, Y. DWARF27, an iron-containing protein required for the biosynthesis of strigolactones, regulates rice tiller bud outgrowth. Plant Cell 21 (2009) 1512-1525. [PMID: 19470589]

2. Alder, A., Jamil, M., Marzorati, M., Bruno, M., Vermathen, M., Bigler, P., Ghisla, S., Bouwmeester, H., Beyer, P. and Al-Babili, S. The path from β-carotene to carlactone, a strigolactone-like plant hormone. Science 335 (2012) 1348-1351. [PMID: 22422982]

[EC created 2012]

Continued with EC 5.3.1 to EC 5.3.2
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