Studies on the Enzyme Synthesizing the Aromatic Product Alternariol.

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Abstract
The properties of an alternariol synthesizing enzyme from Alternaria tenuis have been investigated with regard to the influence of time and enzyme concentration on the reaction. Optimum activity was obtained at pH 7.8-7.9 at 28[degree]C. No activation of the enzyme was observed with the metal ions tested but Zn2+ and Cu3+ inhibited the reaction. Inhibition was also obtained with the usual SH-reagents, poly-[beta]-keto compounds, and coenzyme A as well. On the other hand, the thiol compounds glutathione and cysteine stimulated the reaction. Excess of acetyl coenzyme A was found to inhibit the enzyme activity when using malonylpantetheine as cosubstrate. Similarly, increasing amounts of malonyl coenzyme A inhibits the formation of alternariol at constant concentrations of acetyl coenzyme A or acetylpantetheine. Km for acetyl coenzyme A, acetylpantetheine and malonylpantetheine have been determined by using various combinations of the substrates. Of a number of coenzyme A derivatives tested only propionyl coenzyme A was able to replace acetyl coenzyme A in the condensation with malonyl coenzyme A.
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