Inhibitory actions of mercury compounds against glucose-6-phosphate dehydrogenase from yeast

Kinetic studies on the inhibition of the activity of glucose-6-phosphate dehydrogenase with mercuric chloride (MC) and methylmercuric chloride (MMC) have revealed that MC inhibited the enzyme non-competitively, while MMC inhibited it competitively. The Km value was 5.26 X 10(-5) M for glucose-6-phosphate and Ki value of MC was 2.17 X 10(-5) M, while that of MMC was 4.35 X 10(-3) M. The strong complex formation of nicotinamide adenine dinucleotide phosphate (NADP) or amino acids (cysteine, cystine, histidine, tryptophan or tyrosine) with MC was demonstrated in the presence of phosphate buffer as compared with that of MMC in the same buffer.