CONVERSION OF D-HAMAMELOSE INTO 2-CARBOXY-D-ARABINITOL AND 2-CARBOXY-D-ARABINITOL 1-PHOSPHATE IN LEAVES OF PHASEOLUS-VULGARIS L

[1-C-14]Hamamelose (2-hydroxymethyl-D-ribose) was synthesized by react ion of ribulose B-phosphate with potassium [C-14]cyanide, catalytic hy drogenation of the resulting cyanohydrin, and dephosphorylation of the product, Its identity was established by a chromatographic comparison with hamamelose isolated from the bark of witch hazel (Hamamelis virg iniana L.). Following vacuum infiltration of the [1-C-14]hamamelose in to leaf discs from Phaseolus vulgaris L., C-14-labeled 2-carboxy-D-ara binitol (CA) and 2-carboxy-D-arabinitol 1-phosphate (CA1P) were formed , in the dark. Conversion of hamamelose to both CA and CA1P in the lea f discs was inhibited by dithiothreitol and sodium fluoride, although at high concentrations of these inhibitors conversion into CA was stil l evident when conversion into CA1P was totally inhibited. Wheat (Trit icum aestivum L.) leaves converted hamamelose into CA without formatio n of CA1P, Leaves from P. vulgaris contained 68 nmol . g(-1) fresh wei ght of hamamelose in the light and 35 nmol . g(-1) fresh weight in the dark, A pathway for the biosynthesis of CA1P from Calvin cycle interm ediates is proposed which includes the sequence: hamamelose --> CA --> CA1P.