beta-mercapto-alpha-ketoglutarate was a potent inhibitor , competitive with isocitrate and noncompetitive with nadp+ , of the mitochondrial nadp-specific isozyme from pig heart ( ki = 5 nm ; km ( dl-isocitrate ) /ki ( rs-beta-mercapto-alpha-ketoglutarate ) = 650 ) and pig liver , the cytosolic isozyme from pig liver ( i0.5 = 23 nm ) , and the nadp-linked enzymes from yeast ( ki = 58 nm ) and escherichia coli ( ki = 58 nm ) at ph 7.4 and with mg2+ as activator . beta-mercapto-alpha-ketoglutarate was also an effective inhibitor of nadp-isocitrate-dehydrogenase activity in intact liver mitochondria . beta-mercapto-alpha-ketoglutarate was a much less potent inhibitor for heart nad-isocitrate dehydrogenase ( ki = 520 nm ) than for the nadp-specific enzyme . beta-methylmercapto-alpha-ketoglutarate ( i0.5 = 10 microm ) was a much less effective inhibitor than the beta-mercapto derivative for heart nadp-isocitrate dehydrogenase .
C0022173
isozyme
C0014442
enzyme