Use of deuterium labelled glucose in evaluating the pathway of hepatic glycogen synthesis.

Deuterium labelled glucose has been used to study the pathway of hepatic glycogen synthesis during the fasted-refed transition in rats. Deuterium enrichment of liver glycogen was determined using nuclear magnetic resonance as well as mass spectroscopy. Sixty minutes after oral administration of deuterated glucose to fasted rats, the portal vein blood was fully enriched with deuterated glucose. Despite this, less than half of the glucose molecules incorporated into liver glycogen contained deuterium. The loss of deuterium label from glucose is consistent with hepatic glycogen synthesis by an indirect pathway requiring prior metabolism of glucose. The use of deuterium labelled glucose may prove to be a useful probe to study hepatic glycogen metabolism. Its use may also find application in the study of liver glycogen metabolism in humans by a noninvasive means.

Proton hyperfine resonance assignments in cyanide-ligated cytochrome c peroxidase using the nuclear Overhauser effect.

The development of the proton nuclear Overhauser effect (NOE) for hyperfine shifted resonances of cyanide-ligated cytochrome c peroxidase (Saccharomyces cerevisiae) has been studied. In the pre-steady state regime, the major effects are due to primary NOEs to nearest neighbor protons. This has been used to advantage in making assignments of all of the remaining unassigned, resolved, downfield hyperfine shifted resonances. This work also determined the relative orientation of the heme pyrrole II substituents which is the cis configuration with the 4 alpha-vinyl proton pointing away from the 3CH3. In addition to heme protons, resonances of histidine 175, threonine 180, and histidine 52 have been assigned. These results indicate some structural rearrangement of the distal amino acids accompanying ligation.