Effect of Nitrogen-Source on Hydrazidase Activity

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Hydrazidase activity of isoniazid-resistant cells of Mycobacterium avium (strain AVT) was studied, when the nitrogen source had been modified quantitatively or qualitatively. Fig. 1 shows the effects of amount of aspara gine in media. Growth of the resistant cells on the asparagine-poor medium (2gm. per 1.) was not poorer than that on the ordinary Sauton medium (4gm. per 1.) at the early stages, but became gradually slower, and the maximal yield was almost 60% of that from ordinary Sauton medium. Growth was poor on the asparagine-enriched medium (20gm. per 1.). Hydrazidase activity was remarkably high by the asparagine-poor medium and, on the con trary, almost no activity was observed by the enriched medium. These effects on hydrazidase activity and on cell-growth were not specific for asparagine, but was observed by the addition of amino-acids mixture, consisting of 1-arginine, 1-histidine, 1-isoleucine, 1-leucine, 1-lysine, 1-methionine, 1-phenylalanine, 1-threonine, 1-tryptophane, 1 valine and glycine. (Fig. 2) When ammonium salt was used as sole nitro gen source, growth of bacilli was as well as on the asparagine medium at the early stages, but became poorer gradually and the maximal yield was about half of that from asparagine medium. Hydrazidase activity was remarkably high at the early stage and reached as five times higher as the maximal activity by asparagine medium. The experimental results, where the nitrogen source was one of amino-acids other than aspara gine or of proteins, were summarized in Figs. 4 and 5, respectively. Amino-acids, such as glutamic acid, glycine, and tryptophane, and proteins, such as bovine serum albumine fraction, horse serum, and beef-extract, did not support the growth of resistant cells, which have been sub cultured on asparagine media, when used as sole nitrogen source. Hydrazidase activity was assayed only by glutamic acid medium and by beef extract medium, and in either cases activ ity was higher than in the case of asparagine medium. These experimental results reported in this paper suggested that hydrazidase activity of the resistant cells was higher when cultured on the media, which contained smaller amount of nitrogen source quantitatively or poorer nitrogen source for cell-growth qualitatively. The provable mode of action of isoniazid and mechanism of resistance against isoniazid and, in this connection, biological significance of hydrazidase were discussed.
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Effect of Nitrogen-Source on Hydrazidase Activity

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