E. W. Putman

Formation and interconversion of sugar nucleotides by plant extracts

Abstract Extracts from mung bean seedlings and from a number of other plants contain a pyrophosphorylase (or pyrophosphorylases) capable of catalyzing the reversible formation of sugar nucleotides from UTP and a number of sugar 1-phosphates, according to the following reaction: UTP + S-1-P UDPS + PP. UDPG, UDPGal, UDPXy, and UDPAr are formed in this reaction from α- d -G-1-P, α- d -Gal-1-P, α- d -Xy-1-P, and α- and β- l -Ar-1-P, respectively. The reaction requires a bivalent metal ion (Mg ++ , Mn ++ , or CO ++ ). Sugar nucleotides are not formed from β- d -G-1-P, β- d -Gal-1-P, β- d -Xy-1-P, α- d -Ar-1-P, α-, β- l -Ar(F)-1-P, or α- d -Ar(F)-1-P. No exchange between PP and UTP 32 can be demonstrated except in the presence of one of the reactive sugar 1-phosphates. Mung bean seedling extracts also catalyze the interconversion of UDPG and UDPGal and of UDPXy and UDPAr.

Metabolism of galactose in canna leaves and wheat seedlings

Abstract The transformation of randomly 14 C-labeled galactose was studied in Canna leaf disks during the course of a 3· hour respiration period in the dark. Introduction of this radioactive sugar into Canna leaf tissue caused a rapid appearance of 14 C-labeled sucrose and 14 C-labeled hexose monophosphates. When the radioactive sucrose was hydrolyzed to its monosaccharide constituents, the activity of the glucose was equal to that of fructose. The major proportion of the radioactive phosphorylated hexoses isolated from Canna leaf tissue, after infiltration of randomly 14 C-labeled galactose was an easily hydrolyzable galactose phosphate, which is probably galactose-1-phosphate. When galactose-1- 14 C was introduced into wheat seedlings and the glucose isolated from the sucrose after 2 hours was degraded to its individual carbon atoms, C-1 contained the major proportion of the activity (72%). C-6 contained practically all the remainder of the label (21%) which may have been produced through randomization with C-1 by a reversal of the glycolytic system in the respiring plant. The other four carbon atoms in the glucose chain possessed very little activity. The data indicate that galactose is converted directly to glucose without prior degradation of the chain, probably through a mechanism involving the enzyme, galactowaldenase.

Distribution of radioactivity in photosynthetically prepared C14-labeled glucose

Abstract C 14 -labeled glucose isolated from the Canna indica plant after a 24-hr. photosynthetic period in the presence of C 14 O 2 was assayed for the activity of the various carbon atoms. Employing purely chemical methods, the C 14 activity of each of the six carbon atoms of the glucose molecule was found to be the same.