ID 3.7.1.12 DE cobalt-precorrin 5A hydrolase. CA Co-precorrin-5A + H2O = acetaldehyde + Co-precorrin-5B + H(+). CC -!- This enzyme hydrolyzes the ring A acetate delta-lactone of cobalt- CC precorrin-5A resulting in the loss of the C-20 carbon and its CC attached methyl group in the form of acetaldehyde. CC -!- This is a key reaction in the contraction of the porphyrin-type CC tetrapyrrole ring and its conversion to a corrin ring in the CC anaerobic (early cobalt insertion) adenosylcobalamin biosynthesis CC pathway. DR Q58544, CBIG_METJA ; O87697, CBIG_PRIMG ; Q05631, CBIG_SALTY ; //