Purification and some properties of aspartate aminotransferase of Methanobacterium thermoformicicum SF-4.

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Abstract
Aspartate aminotransferase (AAT) of Methanobacterium thermoformicicum SF-4 was purified to a homogeneous state on polyacrylamide gel electrophoresis (PAGE) by DEAE-cellulose, Polybuffer Exchanger (PBE), Phenyl-Sepharose, and hydroxyapatite column chromatography. The molecular weight of the enzyme was estimated to be 57, 000 by both gel filtration and PAGE on a gradient gel. Subunit analysis by sodium dodecyl sulfate (SDS)-PAGE suggested its existence as a single polypeptide with a molecular weight of 50, 000. The enzyme showed its maximum activity at 60°C and at pH 8.5. The activity did not decrease to any extent after heat treatment at 70°C for 1hr at pH 7.5. Transamination activity on L-glutamate was about 4 times higher than that on L-aspartate and was also observed weakly on L-cysteine. Maleate was the most effective inhibitor, while glutarate and fumarate were less effective inhibitors.

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