Safety evaluation of yeast glutaminase

The consumption of soy and soy products (including soy sauce) has been incr easing in Western countries due to purported health benefits of soy (cancer protective, estrogenic effects). In addition to providing soy proteins and isoflavones, soy sauce also functions as a flavor enhancer and is able to impart a "umami" taste. Glutaminases are used in the production of soy sauc e and enzymatically hydrolyzed protein. The glutaminases described herein a cre produced from the cultured broth of Cryptococcus albidus (ATCC-20293) w hich is designated as CK, a mutant of C, albidus (ATCC-20293) which is desi gnated as CK-D10 and the newly isolated Cryptococcus sp. NISL-3771 which Is designated as TK. All three preparations (CK, CK-D10 and TK) were evaluate d for pathogenicity and virulence in mice and were found to be non-pathogen ic. The acute LD(50)s for CK in male mice was greater than 4.8 g/kg body we ight and for female mice was greater than 6.5 g/kg body weight. Acute LD(50 )s for CK and CK-D10 in male and female rats was greater than 7.5 g/kg body weight, and that for TK was greater than 10 g/kg body weight. Subchronic ( 90-day) feeding studies (wherein the glutaminases were presented as dietary admixtures) were conducted in mice and rats. The NOAEL for CK in mice was 7.5 g/kg body weight/day. The NOAELs in rats were as follows: for CK, 9 g/k g body weight/day; for CK-D10, 1.2 g/kg body weight/day, and for TK, 8 g/kg body weight/day, Mice received CK as a dietary admixture at levels of 0, 1 .0 and 10.0% for 1 year, The NOAEL was 13 g/kg body weight/day. The glutami nases from C. albidus described herein demonstrate very low toxicity. (C) 2 000 Published by Elsevier, Science Ltd.