Genes of succinyl-CoA ligase from Saccharomyces cerevisiae

Succinyl-CoA ligase (succinyl-CoA synthetase) catalyzes the nucleotide-depe ndent conversion of succinyl-CoA to succinate. This enzyme functions in the tricarboxylic acid (TCA) cycle and is also involved in ketone-body breakdo wn in animals. The enzyme is composed of alpha and beta subunits that are r equired for catalytic activity. Two genes, LSC1 (YOR142W) and LSC2 (YGR244C ), with high similarity to succinyl-CoA ligase subunits from other species were isolated from Saccharomyces cerevisiae. The expression of these genes was repressed by growth on glucose and was induced threefold to sixfold dur ing growth on nonfermentable carbon sources. The LSC genes were deleted sin gly and in combination. Unlike other yeast strains with defects in TCA cycl e genes, strains lacking either or both LSC genes were able to grow with ac etate as a carbon source. However, growth on glycerol or pyruvate was impai red. An antiserum against both subunits of the Escherichia coli enzyme was capable of recognizing the yeast succinyl-CoA ligase a subunit, and this ba nd was absent in Delta lsc1 deletion strains. Succinyl-CoA ligase activity was absent in mitochondria isolated from strains deleted for one or both LS C genes, but activity was restored by the presence of the appropriate LSC g ene on a plasmid. The yeast succinyl-CoA ligase was shown to utilize ATP bu t not GTP for succinyl-CoA synthesis.