Effect of 3-amino-1,2,4-triazole on histidine metabolism in algae.

Growth of Chlorella vulgaris and Prototheca zopfii is inhibited by treatment with 3-amino-1,2,4-triazole. Growth of these 2 algae in the presence of amino triazole is accompanied by the accumulation in the culture media of the dephosphorylated histidine precursor, imidazoleglycerol. The addition of histidine to the culture media in the presence of amino triazole restored the normal growth rates of these organisms and reduced the accumulation of imidazoleglycerol. These data suggest that amino triazole inhibits the synthesis of histidine by interfering with the activity of the enzyme, imidazoleglycerol phosphate dehydrase.