Product inhibition of the cysteine sulfoxide lyase of tulbaghia violacea

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Abstract

Tulbaghia violacea Harv. contains a pyridoxal phosphate-requiring enzyme which catalyzes the cleavage of S-ethyl-l-cysteine sulfoxide to ethyl ethanethiosulfinate, pyruvate, and ammonia. This enzyme is similar to the alliin alkyl sulphenate-lyase (alliinase) of Allium sativum L. (garlic). In vitro the reaction ceased when only a small percentage of the substrate had been transformed, and inhibition of the enzyme activity obeyed first-order kinetics irrespective of the amount of enzyme or substrate present. Also, the amount of substrate transformed at termination of reaction was curvilinearly related to the amount of enzyme present. The rate of enzyme inactivation, as measured by t12, was dependent on the rate of reaction rather than on substrate concentration. The data indicate that the inactivation is a result of substrate cleavage, but none of the end products of reaction are inhibitors of the enzyme. The similarity of the findings to those reported for other α, β elimination reactions involving pyridoxal phosphate enzymes is discussed. It is proposed that the inhibition of these reactions is similar to that of the lyase and is caused by an unstable precursor of pyruvate which interacts with the pyridoxal phosphate of the holoenzyme.

References (14)

  • J. Caravaca et al.

    Biochem. Biophys. Res. Commun

    (1959)
  • S. Grisolia et al.

    Biochem. Biophys. Res. Commun

    (1959)
  • E.E. Snell

    Vitamins and Hormones

    (1958)
  • W.A. Wood et al.

    J. Biol. Chem

    (1949)
  • L. Davis et al.

    J. Biol. Chem

    (1962)
  • J.A. Nishimura et al.

    J. Biol. Chem

    (1961)
  • S. Schwimmer et al.

    Arch. Biochem. Biophys

    (1963)
There are more references available in the full text version of this article.

Supported in part by National Science Foundation Grant G-15910.

2

Present address: Division of Plant Industry, C.S.I.R.O., Canberra, Australia.

3

Department of Vegetable Crops, University of California, Davis, California 95616.

4

Department of Food Science and Technology, University of California, Davis, California 95616.

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