Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

Abstract

A strain of Neurospora crassa defective in amino acid transport can utilize a variety of amino acids for growth when readily metabolizable nitrogen is limiting. Growth is accompanied by the production of an extracellular deaminase that converts the amino acid to its respective keto acid plus equimolar quantities of utilizable nitrogen in the ammonium ion form. Production of the deaminase is subject to ammonium repression. The relationship between the ability of an amino acid to trigger deaminase production and the presence of particular amino acid permease deficiencies is complex. Four classes of amino acids have been defined with respect to this relationship. The existence of multiple extracellular deaminases is discussed.

Regulation of amino acid utilization in Neurospora crassa: effect of nmr-1 and ms-5 mutations

“…The ms-S mutation appeared to confer slightly greater insensitivity to glutamine repression than did the nmr-l mutation. Growth of all strains was within the range normally observed for strains able to utilize these amino acids as sole nitrogen sources (10). Typical growth data are displayed in Fig.…”

“…The pmn; pmb; pmg strain of N. crassa produces an extracellular deaminase in response to nitrogen limitation plus the presence of an amino acid (12). Production of this enzyme is prevented by glutamine-mediated nitrogen metabolite repression (10,11). The details of the mechanism by which amino acid utilization occurs in this transport-defective strain are not fully known, but it is believed that the degradation of the amino acid to its keto acid and ammonium ion components provides the necessary nitrogen (10,11).…”

“…Production of this enzyme is prevented by glutamine-mediated nitrogen metabolite repression (10,11). The details of the mechanism by which amino acid utilization occurs in this transport-defective strain are not fully known, but it is believed that the degradation of the amino acid to its keto acid and ammonium ion components provides the necessary nitrogen (10,11). Transport of these components by their respective transport systems allows for potential internal reconstitution of the amino acid molecule.…”

“…The nitrogen-deficient Vogel medium served as the basal salts medium to which various secondary nitrogen sources were added as indicated below. Assays were performed at 35°C as described by DeBusk et al (10,12).…”

Crystallization and preliminary X-ray analysis of a bacterialL-amino-acid oxidase fromRhodococcus opacus

“…Little is known about the function of LAAOs from prokaryotes and lower eukaryotes. LAAO from the fungus Neurospora crassus is induced by lack of readily metabolizable nitrogenous compounds in the presence of l-arginine and l-phenylalanine (DeBusk & Ogilvie, 1984). The LAAO from Chlamydomonas reinhardtii is induced if there is no primary nitrogen source available to produce ammonia (Munoz-Blanco et al, 1990).…”