Indoleacetaldoxime hydro-lyase : II. Purification and properties

Shukla, PS and Mahadevan, Subramony (1968) Indoleacetaldoxime hydro-lyase : II. Purification and properties. In: Archives of Biochemistry and Biophysics, 125 (3). pp. 873-883.

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Abstract

The purification and some properties of the enzyme indoleacetaldoxime hydrolyase (EC 4.2.1.29) from the fungus Gibberella fujikuroi, which dehydrates indoleacetaldoxime (IAOX) to indoleacetonitrile (IAN), are described. The enzyme activity in the fungus is present only under certain culture conditions. It is a soluble enzyme, has an optimum pH at 7, shows an energy of activation of —15,670 cal/mole, and has a Michaelis constant of 1.7 × 10−4 Image at 30 °. It appears to be specific for IAOX, and 1 mole of IAN is produced per mole of IAOX utilized. The enzyme is inhibited by a number of aldoximes of which phenylacetaldoxime (PAOX) is the most potent inhibitor. Inhibition by PAOX is competitive (Ki = 2.2 × 10−8 Image ). The enzyme is inhibited by SH reagents such as p-hydroxymercuribenzoate and N-ethylmaleimide, and by a number of SH compounds such as cysteine, β-mercaptoethanol, and 2,3-dimercaptopropanol (BAL). However, glutathione activates the enzyme. Metal chelating agents such as 8-OH-quinoline and diethyl dithiocarbamate inhibit the enzyme; the inhibition is partly reversed by ferric citrate. Ascorbic acid, and particularly dehydroascorbic acid (DHA), are good activators of the enzyme. Several other biological oxidants had either no action or had a slight effect. Potassium cyanide activates the enzyme at low concentration but inhibits at higher concentrations. Reduction of the enzyme with NaBH4 reduces activity, and the effect is partly reversed by pyridoxal phosphate and also by DHA. The above properties indicate that both an SH function and an oxidized function are required for activity.

Item Type:	Journal Article
Publication:	Archives of Biochemistry and Biophysics
Publisher:	Elsevier Science
Additional Information:	Copy right of this article belongs to Elsevier Science.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	14 May 2010 05:28
Last Modified:	19 Sep 2010 06:06
URI:	http://eprints.iisc.ac.in/id/eprint/27731

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