Properties of 3-hexulose phosphate synthase and phospho-3-hexuloisomerase of a methanol-utilizing bacterium, 77a.

Abstract

The key enzymes, 3-hexulose phosphate synthase and phospho-3-hexuloisomerase, of the pentose monophosphate pathway for formaldehyde fixation were purified from a methanolgrown bacterium 77a, and their enzymatic properties were investigated. The condensation product between formaldehyde and d-ribulose 5-phosphate by 3-hexulose phosphate synthase was identified as d-arabino-3-hexulose 6-phosphate, on the bases of UV-absorption spectrum, pH stability and color reactions with several reagents on thin-layer chromatography. The apparent Km value of 3-hexulose phosphate synthase for each substrate was determined: formaldehyde, 0.74; d-ribulose 5-phosphate, 0,081; d-arabino-3-hexulose 6-phosphate, 0.036 mm. The apparent Km values of phospho-3-hexuloisomerase for d-arabino-3-hexulose 6-phosphate and d-fructose 6-phosphate were found to be 0.029 and 0.67 mm, respectively.No activity of phospho-3-hexuloisomerase was able to detect in the cell-free extract of methanol-utilizing yeasts, Kloeckera sp. No. 2201 and Hans...