Effect of External and Intramolecular Nucleophiles on Nature of Products of Carboxypeptidase A-Catalyzed Hydrolysis of Esters. Attempted Trapping of Acyl-Enzyme Intermediate

카르복시펩티다제A의 에스테르 가수분해 반응생성물의 종류에 대한 외부 및 분자내 친핵체의 영향. 아실-효소중간체의 포획시도

  • 서정헌 (서울대학교 자연과학대학 화학과) ;
  • Published : 1978.06.30

Abstract

Carboxypeptidase A-catalyzed hydrolysis of ester substrates was carried out at room temperature in the presence of a number of external reagents. If the acyl-enzyme intermediate, an anhydride, is attacked by the external reagents, products formed by trapping at the acyl portion or at the enzyme portion of the anhydride group can be obtained. Examination of the uv/vis spectral properties of the reaction products and of changes in enzyme activity indicated that such trapping reactions did not occur. Also performed was evaluation of enzymatic rate parameters for the the hydrolysis of O-(o-hydroxyphenylacetyl)-L-${\beta}$-phenyllactate. Detection of 2-coumaranone possibly formed by attack of the o-hydroxy group as an intramolecular trapping group at the acyl-enzyme intermediate was tried, but no evidences for the intramolecular trapping reaction were obtained. Failure to trap the intermediate was discussed in terms of steric hindrance imposed on the approach of the trapping reagents to the anhydride group of the acyl-enzyme intermediate and of the fast enzymatic breakdown of the intermediate.

Keywords

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