The masked cysteine residues in methylmalonyl-CoA mutase from Propionibacterium shermanii are essential for catalytic activity

AbstractTwo masked cysteine residues have been reported in methylmalonyl-CoA mutase from Propionibacterium shermanii, Cys-535 in the α-subunit and Cys-517 in the β-unit, which are revealed only after reduction of the denatured enzyme with dithiothreitol. It has been postulated that these residues are involved in disulphide linkages to unknown thiols of low Mr. These two masked cysteine residues have been changed to an alanine, individually. Both the mutants, C535αA and C517βA, were inactive. This shows that both these residues are essential for catalytic activity