Oct 1, 1975

Intramolecular arsanilazotyrosine-248-Zn complex of carboxypeptidase A: a monitor of catalytic events

Proceedings of the National Academy of Sciences of the United States of America
L W HarrisonB L Vallee


The intensely chromophoric intramolecular coordination complex formed between arsanilazotyrosine-248 and the active site zinc atom of azocarboxypeptidase A (Johansen, J. T. & Vallee, B. L. (1971) Proc. Nat. Acad. Sci. USA 68, 2532-2535) is a spectrokinetic probe of catalytic events. The interconversion of the azoTyr-248-Zn complex and its constituents is measured by stopped-flow pH and temperature-jump methods. The rate of interconversion, 64,000 sec-1, is orders of magnitude faster than that of the catalytic step itself (about 0.01-100 sec-1). Rapidly turned over peptide and ester substrates disrupt the azoTyr-248-Zn complex before hydrolysis occurs. As a consequence, formation of azoTyr-248, substrate binding, and catalysis can all be monitored while catalysis is actually in progress. The results of these dynamic studies specify a course of catalytic events, different from those postulated based on x-ray structure analysis. If azoTyr-248 is displaced, the direction is opposite to the inward movement postulated on the basis of x-ray studies and is not unique to induction by substrates, since rapid changes in pH also result in analogous spectral changes. AzoTyr-248 carboxypeptidase has all the features which are essential for m...Continue Reading

  • References11
  • Citations6


  • References11
  • Citations6


Mentioned in this Paper

Carboxypeptidase A
Activated T Cell Autonomous Cell Death
Plain X-ray
Carboxypeptidase A Activity
Plasma Protein Binding Capacity
Radiographic Imaging Procedure
Carboxypeptidase [EPC]

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