EC Explorer

1.21.98.3

anaerobic magnesium-protoporphyrin IX monomethyl ester cyclase

magnesium-protoporphyrin IX 13-monomethyl ester + 3 S-adenosyl-L-methionine + H₂O = 3,8-divinyl protochlorophyllide a + 3 5′-deoxyadenosine + 3 L-methionine (overall reaction);;(1a) magnesium-protoporphyrin IX 13-monomethyl ester + S-adenosyl-L-methionine + H₂O = 13¹-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + 5′-deoxyadenosine + L-methionine;;(1b) 13¹-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + S-adenosyl-L-methionine = 13¹-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + 5′-deoxyadenosine + L-methionine;;(1c) 13¹-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + S-adenosyl-L-methionine = 3,8-divinyl protochlorophyllide a + 5′-deoxyadenosine + L-methionine

bchE (gene name), MPE cyclase (ambiguous)

magnesium-protoporphyrin-IX 13-monomethyl ester,S-adenosyl-L-methionine:H₂O oxidoreductase (hydroxylating)

This radical AdoMet enzyme participates in the biosynthesis of chlorophyllide a in anaerobic bacteria, catalysing the formation of an isocyclic ring. Contains a [4Fe-4S] cluster and a cobalamin cofactor. The same transformation is achieved in aerobic organisms by the oxygen-dependent EC 1.14.13.81, magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase. Some facultative phototrophic bacteria, such as Rubrivivax gelatinosus, possess both enzymes.

created 2016