Pseudomonas fluorescens Malate Synthase 의 Acetyl - CoA 결합부위에 있는 필수 Cysteine 잔기에 대한 입증 = Evidences for a Catalytically Essential Cysteinyl Residue at Acetyl - CoA Binding Region of Pseuodmonas fluorescens Malate Synthase

다국어 초록 (Multilingual Abstract)

Malate synthase from Pseudomonas fluorescens was inhibited by iodoacetamide and N-ethylmaleimide with second-order rate constant of 43.9 M^(-1) and of 1,784 M^(-1), respectively. A double logarithmic plot of the reciprocal of the half-time of inactivation against concentration yield reaction order of 1.275 and 0.94 with respect to iodoacetamide and N-ethylmaleimide, respectively, indicating that there may be one essential residue per active enzyme. The enzyme was also rapidly inhibited by 5,5`-dithiobis (2-nitro-benzoic acid) and by 2-nitro-5-(thiocyanato)benzoate. pK_a of the functional group was determined to be 8.3 by using iodoacetamide. The inactivation by iodoacetamide and by N-ethylmaleimide was protected by acetyl-CoA but not by glyoxylate. The total number of thiol groups in the enzyme was determined to be five. These results strongly suggest that there is one essential group at the acetyl-CoA binding region among five thiol groups of the malate synthase.