Hydrolases;
Acting on ester bonds;
Carboxylic-ester hydrolases
Sysname
pheophorbide-a hydrolase
Reaction(IUBMB)
pheophorbide a + H2O = pyropheophorbide a + methanol + CO2 (overall reaction) [RN:R08974];
(1a) pheophorbide a + H2O = C-132-carboxypyropheophorbide a + methanol [RN:R08975];
(1b) C-132-carboxypyropheophorbide a = pyropheophorbide a + CO2 (spontaneous) [RN:R08976]
pheophorbide a [CPD:C18021];
H2O [CPD:C00001];
C-132-carboxypyropheophorbide a
Product
pyropheophorbide a [CPD:C18064];
methanol [CPD:C00132];
CO2 [CPD:C00011];
C-132-carboxypyropheophorbide a
Comment
This enzyme forms part of the chlorophyll degradation pathway, and is found in higher plants and in algae. In higher plants it participates in de-greening processes such as fruit ripening, leaf senescence, and flowering. The enzyme exists in two forms: type 1 is induced by senescence whereas type 2 is constitutively expressed [1,2]. The enzyme is highly specific for pheophorbide as substrate (with a preference for pheophorbide a over pheophorbide b) as other chlorophyll derivatives such as protochlorophyllide a, pheophytin a and c, chlorophyll a and b, and chlorophyllide a cannot act as substrates [2]. Another enzyme, called pheophorbide demethoxycarbonylase (PDC), produces pyropheophorbide a from pheophorbide a without forming an intermediate although the precise reaction is not yet known [1].
