Lysine fermentation to fatty acids and ammonia: a cobamide coenzyme-dependent process.

This is a balanced oxidation-reduction process and, as judged by isotope experiments, differs from the established pathways of lysine degradation occurring in animals, Neurospora, and certain bacteria. Numerous technical problems encountered in attempts to study the reaction in cell-free extracts of C. sticklundii prompted us to isolate a new Clostridiumr from soil enrichment cultures containing lysine as the fermentable substrate.2 Fresh cell suspensions of the Ecuadorian Clostridium, like those of C. sticklandii (3), degrade lysine by two independent pathways, as indicated by the fact that acetate and butyrate are each formed in approximately equal amounts from either end of the lysine molecule (Table I). Soluble extracts of the Ecuadorian Clostridium are also capable of degrading both lysine isomers but, unlike the intact cells, employ only one of the two degradative pathways; i.e. acetate is derived solely from the carboxyl end of the molecule (Table I). Thus 2-Cl*-lysine yields Cr4-acetate and unlabeled butyrate, whereas Ci4-butyrate and unlabeled acetate are obtained from 6-C14-lysine.3 Results of some typical experiments demonstrating cofactor requirements of the soluble enzyme system are summarized in Table II. As illustrated by the data of Experiment 1, most crude extracts must be supplemented with DPN. After charcoal treatment, the enzyme preparation exhibits a further requirement for a boiled extract of fresh cells (Experiment 2, Table II). The boiled extract has been found to contain three components necessary for lysine degradation. One of these components, anionic in nature, is replaceable with pyruvate but not cr-ketoglutarate or cr-keto-