The formation of 5-phosphomevalonate by mevalonate kinase in Hevea brasiliensis latex

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Abstract
Evidence has been produced for the formation of 5-phosphomevalonate from potassium DL-mevalonate by the latex of Hevea brasiliensis and by reconstituted freeze-dried serum obtained from this latex. The enzyme, mevalonate kinase, catalysing the formation of 5-phosphomevalonate from potassium DL-mevalonate and ATP has been partially purified. 5-Phospho-mevalonate formed by the purified mevalonate kinase from potassium [2-C14]mevalonate has been shown to be incorporated by latex into rubber to about 2.4 times the extent of DL-mevalonate. The enzyme can utilize inosine triphosphate as effectively as adenosine triphosphate as a phosphate donor and is also slightly active with uridine triphosphate. The enzyme was fairly stable to a range of pH values and temperatures, the activity being optimum at pH 7.5 and 60-70[degree]. The energy of activation was 10.7 kcal./mole. The Km values were 0.13 m[image]-for potassium DL-mevalonate and 2.0 m[image] for ATP at 30[degree]. The enzyme required the presence of Mn2+ (4m[image]X which was less effective, and by Ca2+, which was far less effective. Although the enzyme did not require cysteine or reduced glutathione for activation in aerobic conditions, it was inhibited by reagents known to react with thiol groups.