Isolation and Identification of ß-Lysine as an Intermediate in Lysine Fermentation

From the ¹ From the Department of Biochemistry, University of California, Berkeley, California 94720

Clostridium SB4 ferments lysine to acetate, butyrate, and 2 moles of ammonia. The fermenting system appears to be typical of those studied previously (1–7), except that -ketoglutarate is required for fermentation by cell extracts rather than pyruvate.

The omission of all required cofactors except -ketoglutarate and coenzyme A results in the accumulation of a basic amino acid. The amino acid has been isolated in gram quantities and shown to be l-ß,-diaminocaproic acid (l-ß-lysine). The conversion of l-lysine to l-ß-lysine is readily reversible; the equilibrium constant (k = [ß-lysine]/ [lysine]) is 5.7. The level of -ketoglutarate influences both the rate and extent of conversion of lysine to ß-lysine, but the system does not require substrate levels of -ketoglutarate. Pyridoxal phosphate can be substituted for -ketoglutarate when crude cell extracts are used, and -ketoglutarate can be deleted from reaction mixtures without loss of activity when dialyzed extracts are used. A sulfhydryl compound, i.e. glutathione or mercaptoethanol, and coenzyme A are required for maximal rates of conversion of lysine to ß-lysine when dialyzed cell extracts are used. Pyridoxal phosphate has a stimulating effect with such extracts.

ß-Lysine is fermented more rapidly than lysine by Clostridium SB4 extracts, and the addition of lysine does not inhibit ß-lysine fermentation. Apparently ß-lysine lies on or very close to the path of lysine fermentation.

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