Zur Biosynthese der Apiose I

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Abstract
The biosynthesis of apiose in parsley (Apium petroselinum) was investigated by feeding different labeled precursors to shoots of young parsley plants. Apiin was isolated and the distribution of activity between apigenin, apiose and glucose was determined. The radioactivity in C-31 of apiose was determined by periodate oxidation of apiin, and a degradation of apiose-benzylphenylhydrazone yielded the radioactivity in C-1 + C-2. C-3 and C-31 or C-4 of this sugar. The results show that acetate or formate are not precursors for apiose but that all 5 C-atoms of apiose are derived from glucose. Since with glucose-[3,4-14C] as the source of radiocarbon 45% of the radioactivity is located in C-3 and 40% in C-31 of apiose, C-31 of this sugar must originate either from C-3 or C-4 of glucose. Experiments with glucose-[-6-14C-4-T] indicate that C-6 of glucose is lost during its conversion into apiose. 70% of the tritium is located at C-31 in this experiment and with glucose- [U-14C-3-T] as precursor 60% of the tritium is located at C-31. The results can be rationalized by postulating that the biosynthesis of apiose involves UDP-giucuronic acid as an intermediate which is decarboxylated and undergoes an internal rearrangement with expulsion of C-3.

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