Intramolekulare Wasserstoffverschiebung in der Hexosephosphatisomerase-Reaktion bei der photosynthetischen Stärkebildung in Chlorella

Abstract

Chlorella pyrenoidosa was illuminated in the presence of glucose and fructose echa having carbon-14 and tritium markers. Starch and sucrose were degraded to obtain the intramulocular distribution of 14C and tritium. Glucose-1-14C-2-T was incorporated into the glucose of starch and into the glucose moiety of sucrose without change of the T/14C ratio. Fructose-1-14C-1-T (labelled stereospecifically in the isomerase position) was incorporated into starch, yielding predominately glucose-1-14C-2-T, whereas fructose-1-14C-1-T (labelled in the nonisomerase position) gave mainly glucose-1-14C-1-T. The results, in particular the transfer of tritium from C-1 of fructose to C-2 of glucose, are interpreted as being a strong indication for an intramolecular hydrogen transfer in the hexosephosphat-isomerase reaction in a multienzyme system of the photosynthetic starch biosynthesis in vivo, shielding the hexoses of T-exchange reactions with water.