LytB protein catalyzes the terminal step of the 2-C-methyl-D-erythritol-4-phosphate pathway of isoprenoid biosynthesis

Recombinant LytB protein from the thermophilic eubacterium Aquifex aeolicus produced in Escherichia coli was purified to apparent homogeneity. The purified LytB protein catalyzed the reduction of (E)-4-hydroxy-3-methyl-but-2-enyI diphosphate (HMBPP) in a defined in vitro system. The reaction products were identified as isopentenyl diphosphate and dimethylallyl diphosphate. A spectrophotometric assay was established to determine the steady-state kinetic parameters of LytB protein. The maximal specific activity of 6.6 +/- 0.3 mumol min(-1) mg(-1) protein was determined at pH 7.5 and 60degreesC. The k(cat) value of the LytB protein was 3.7 +/- 0.2 s(-1) and the K-m value for HMBPP was 590 +/- 60 muM. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.