Asparagine degradation

Like many other amino acids, asparagine may be utilized by S. cerevisiae as a sole source of nitrogen. Catabolism of asparagine for nitrogen involves the action of asparaginases, which hydrolyze the amide group in the side chain of asparagine. This converts asparagine to aspartate and releases an assimilable molecule of ammonia (NH3). Further nitrogen can be derived from the newly generated aspartate molecule via its reversible conversion to glutamate by aspartate aminotransferases. Glutamate, whose amino group can be hydrolyzed to release ammonia, represents one of the major sources of nitrogen for biosynthetic reactions in S. cerevisiae. SOURCE: SGD pathways, http://pathway.yeastgenome.org/server.html

众多氨基酸之中，天冬酰胺亦然是酿酒酵母（S. cerevisiae）用以氮素单一来源的利用对象。天冬酰胺的氮素代谢过程涉及天冬酰胺酶的作用，该酶催化天冬酰胺侧链中的酰胺基团发生水解。此过程将天冬酰胺转化为天冬氨酸，并释放出可同化的氨分子（NH3）。进一步，氮素还可由新生成的天冬氨酸分子中提取，通过其可逆性转化为谷氨酸的过程实现，此过程由天冬氨酸转氨酶催化。谷氨酸的氨基基团可通过水解作用释放氨，它是酿酒酵母中生物合成反应氮素的主要来源之一。资料来源：SGD通路，http://pathway.yeastgenome.org/server.html