Rhizobium tnifolii에서 정제한 malonyl-CoA synthetase가 2,3-butanedione과 diethylpyro-carbonate(DEP)에 의해 불활성화 되었다. 각 불활성화 반응은 pseudo first-order kinetics으로 나타났다. 2,3-Butanedion에 의한 효소의 불활성화 반응의 2차 속도상수는 pH 8.0, $30^{circ}C$에서 $17.4M^{-1}{cdot}min^{-1}$이었다. DEP에 의해 효소가 빠르게 불활성화되었으며 반응의 2차속도상수는 pH 7.1, $30^{circ}C$ 에서 $780M^{-1}{cdot}min^{-1}$이었다. 각 시약과 반응차수는 1.06과 1.03이였다. ATP가 위의 2가지 시약에 의한 효소의 불활성화를 저해하였다. 이러한 결과들은 malonyl-CoA synthetase의 ATP 결합부위나 그 주위에 효소활성에 필수적인 arginine residue와 histidyl residue가 존재함을 시사한다.
Malonyl-CoA synthetase from Rhizobium trifolii was inactivated by 2,3-butanedione and diethylpyrocarbonate (DEP). In each case, inactivation followed pseudo first-order kinetics. The second-order rate constant for the inactivation by 2,3-butanedione was $17.4M^{-1}{cdot}min^{-1}$ at pH 8.0, $30^{circ}C$. DEP rapidly inactivated the enzyme with the second-order rate constant, $780M^{-1}{cdot}min^{-1}$ at pH 7.1, $30^{circ}C$. The reaction order of inactivation with respect to reagents were 1.06 and 1.03 respectively. The substrate, ATP, afforded the protection against the inactivation of the enzyme caused by the reagent, respectively. These results indicate that arginine and histidyl residues essential for the enzyme activity are located at or near the ATP binding region of the active site.
