Cobalt-precorrin 5A hydrolase (), CbiG (gene)) is an enzyme with systematic name cobalt-precorrin 5A acylhydrolase. This enzyme catalyses the following chemical reaction
This enzyme hydrolyses the ring A acetate delta-lactone of cobalt-precorrin-5A and releases a two-carbon fragment from the macrocyclic corrin ring as acetaldehyde. This is part of the biosynthetic pathway to cobalamin (vitamin B<sub>12</sub>) in anaerobic bacteria such as Salmonella typhimurium and Bacillus megaterium.