The purification and properties of the l-threonine deaminase of the rumen micro-organism LC1

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Abstract
The L-threonine deaminase of the rumen microorganism LC1 was purified over 100-fold from extracts of vacuum-dried cells by successive fractionation with protamine sulfate and ammonium sulfate, gradient elution with ammonium sulfate and fractionation on a calcium phosphate gel-cellulose column. The enzyme has an optimum pH in the range 9.0-10.0. Km values of 6.8 mM and 3.0 mM were obtained for L-serine and L-threonine respectively. D-Threonine appeared to inhibit the enzyme. The ratio of L-serine deaminase activity to L-threonine deaminase activity varied little at different stages of the purification, suggesting that one enzyme attacks both substrates. The purified enzyme, after freeze-drying in the presence of ammonium sulfate or glutathione, required pyridoxal phosphate. Glutathione also appeared to be necessary for maximum activity.
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