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Nuclear magnetic resonance studies of the active site of carboxypeptidase A.

1966; National Academy of Sciences; Volume: 56; Issue: 1 Linguagem: Inglês

10.1073/pnas.56.1.39

1091-6490

Robert Gerson Shulman, Gil Navon, B J Wyluda, D C Douglass, T Yamane,

Hormonal Regulation and Hypertension

Carboxypeptidase A is a proteolytic metalloenzyme which catalyzes the hy- drolysis of specific carboxyl-terminal peptide bonds.1It has a molecular weight of 34,400 and contains one zinc atom per molecule.Coleman and Vallee2 have shown that the zinc can be removed reversibly, or it can be replaced by Co2+, MnI+, Fe2+, or Ni2+.Each of these substituted metalloenzymes has a characteristic, nonzero, enzymatic activity.Chemical evidence indicates3 that the zinc is bound to one sulfhydryl group and probably to the a-NH2 of the N-terminal asparagine.From experiments which show that the apoenzyme is enzymatically inactive,4 and from others which show that inhibitors5 reduce the rate of chemical exchange of the zinc, Vallee has concluded that the metal ion is at the active site of the enzyme, where the inhibitor is bound.Much is known from these and related studies, in- cluding a preliminary structural analysis by X-ray crystallography.6However, from the viewpoint of the metal ion coordination chemistry and the structural de- tails of the active site, there are many unanswered questions which can be settled by magnetic resonance experiments.This paper presents preliminary results of a nuclear magnetic resonance study