Wild-type and mutant forms of homoisocitric dehydrogenase in the yeast Saccharomycopsis lipolytica.
Homoisocitric dehydrogenase (EC 1.1.1.155) has been purified 525-fold from the yeast Saccharomycopsis lipolytica with a yield of 25%. The preparation was judged to be homogeneous by electrophoresis under denaturing and non-denaturing conditions and by isoelectric focusing; it consisted of a single protein with molecular weight of 48000. In the presence of homoisocitric acid, a higher molecular weight was observed, suggesting a dimeric structure for the native enzyme. Complementing mutants devoid of homoisocitric dehydrogenase activity mapped at two closely linked loci (lys9 and lys10). Lys10 mutants displayed NAD-reducing activity, whereas lys9 mutants retained some carboxylating activity. Our results are best explained by the assumption that the active enzyme is a dimer of identical subunits involved in successive dehydrogenation and decarboxylation steps.[1]References
- Wild-type and mutant forms of homoisocitric dehydrogenase in the yeast Saccharomycopsis lipolytica. Gaillardin, C.M., Ribet, A.M., Heslot, H. Eur. J. Biochem. (1982) [Pubmed]
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