抄録
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 77 a, 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, 0.036mM. 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 0.67mM, 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 Hansenula polymorpha DL-1, under the condition tested.
