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The following reaction leading to the synthesis of the trisaccharide umbelliferose was demonstrated in an enzyme preparation from leaves of Aegopodium podagraria L.: sucrose + UDP-gal-(14)C --> umbelliferose-(14)C + UDP. Neither galactinol nor galactose 1-phosphate could replace UDP-gal. Among 10 different sugars tested only sucrose was a suitable galatosyl acceptor.

A glucosyl and a glucosyl-glucan transferase activity from spinach (Spinacia oleracea L. var. Matador) leaves have been partially purified and characterized. The latter activity (fraction 1 after diethylaminoethylcellulose chromatography) is responsible for the transfer of glucosyl as well as of maltosyl, maltotriosyl, and higher homologous residues to glucose giving rise to maltose and the correspondingly larger molecules. This fraction also shows beta-amylase activity. The transfer takes place only to glucose; maltose, as well as other alpha-1,4-glucans, serve as donors. The enzyme fraction 2 is amylase-free and catalyzes only the transfer of glucosyl moieties, again with high acceptor specificity to glucose. Maltose and larger alpha-1, 4-glucans, with the exception of maltotriose and maltotetraose, act as donors. The physiological function of these enzymes may be the formation of oligosaccharide primers for starch synthetase or phosphorylase.

Light-dependent formation of ribulose-1,5 diphosphate is completely inhibited by low concentrations of 3-(3,4-dichlorophenyl)-1,1-dimethylurea which do not severely affect cyclic photophosphorylation. Also in Scenedesmus mutant number 11, capable of cyclic photophosphorylation, cellular ribulose-1,5 diphosphate-levels do not increase upon illumination. When mutant cells are H(2) adapted, however, a light-dependent formation of ribulose-1,5 diphosphate is observed in the presence of H(2). From these results it has been concluded that at least part of the Calvin cycle does not operate in the dark, since a reductant is lacking which is generated in the light.

Salicylaldoxime (2 x 10(-3)m and less) inhibits cyclic photophosphorylation in intact Chlorella cells severely whereas photosynthetic O(2)-evolution and (14)CO(2)-fixation is hardly affected. Cyclic photophosphorylation in vivo was measured by following anaerobic light dependent glucose uptake. A similar difference in susceptibility has been observed with carbonylcyanide-p-trifluoromethoxyphenylhydrazone. Various controls exclude the possibility that the difference in inhibition was caused by differing experimental conditions or, in the case of glucose assimilation, by an inhibition of a reaction other than photophosphorylation.There also exists a great difference in light saturation of cyclic photophosphorylation and photosynthesis. Evidence is reported that at light saturation of glucose uptake light driven cyclic phosphorylation is indeed the limiting reaction.The results are considered as evidence that cyclic photophosphorylation does not contribute ATP stoichiometrically to photosynthetic CO(2)-fixation.

The production of d-lactic acid, a major fermentation product of Scenedesmus obliquus strain D(3), is inhibited by light. This inhibition has been observed in the wild type as well as in Bishop's mutant 11. However, in mutant 8, which lacks photophosphorylation, light stimulated the formation of d-lactic acid.

When cyclic photophosphorylation is inhibited in Chlorella vulgaris cells by carbonylcyanide-trifluoromethoxy phenylhy-drazone, photosynthetic CO(2)-fixation under anaerobic conditions exhibits a distinct lag. Under the same conditions, the light-dependent formation of ribulose diphosphate shows also this lag. It is concluded that cyclic photophosphorylation is required to fill up the pools of phosphorylated intermediates of the Calvin cycle at a time when noncyclic photophosphorylation cannot yet efficiently operate. Under aerobic conditions, the initial energy demand can be accommodated by respiratory ATP or cyclic photophosphorylation or both. Evidence for stoichiometric participation of cyclic photophosphorylation in photosynthesis is still lacking.