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Enzymatic Degradation of Hydroxamate in Rumen Microbes

Biochemistry Laboratory, Indian Veterinary Research Institute, Regional Station, Palampur (H.P) 176 061, India

ABSTRACT

The enzyme responsible for degradation of acetohydroxamic acid was intracellular. Bacterial and not the protozoal fraction contributed the enzyme activity in the rumen. The enzyme was cell bound and required cofactors in the soluble portion of the cell for activity. Optimum pH and temperature were 7.0 and 39°C. The enzyme was heat stable. No loss of activity was observed after heating at 70 and 100°C for 10 and 5 min, respectively. On storing enzyme at 25°C, loss of activity was 50% on 2nd day, and on 3rd day there was complete loss of activity. There was no loss of activity on storing at 8°C for 3 days. The enzyme lost activity on freezing and thawing. The chelating agents and sulfhydryl agents were inhibitory in nature. Lead²⁺ , mercury²⁺, silver²⁺, cadmium²⁺, zinc²⁺, cobalt²⁺, and nickel²⁺ inhibited the enzyme. Manganese²⁺, magnesium ²⁺, and calcium²⁺ did not have any effect as high as 100 mM. Among manganese²⁺, magnesium²⁺, and calcium²⁺, only calcium²⁺ was able to restore activity of ethylenediaminetetraacetate-treated enzyme, suggesting calcium²⁺ was the cofactor. Nitrophenol, (o and p), dinitrophenol (2, 4 and 2, 6), and sodium cyanide were strong inhibitors of the enzyme, whereas glucose and hydroxylamine did not have any effect. The rate of hydrolysis of different hydroxamates was in order: nicotinohydroxamic acid > phenylacetohydroxamic acid > caprylohydroxamic acid > benzohydroxamic acid > acetohydroxamic acid.