The stereospecificity of hydrogen transfer for the pyridine nucleotide has been ascertained for a number of hitherto uninvestigated dehydrogenase reactions. These determinations have been made with the help of appropriate reference enzymes, and of DPN and TPN labeled with tritium at the 4 position of the nicotinamide ring. Evidence is presented that the following enzymes use the same position (i.e., A or a) as yeast alcohol dehydrogenase: DPN-linked formic dehydrogenase from pea seeds, DPN-linked glyoxylic reductase from spinach leaves, TPN-linked glyoxylic reductase from pea seeds, TPN-linked dihydroorotic dehydrogenase from an aerobic bacterium, and TPN-linked malic enzyme from liver. The opposite stereospecificity (B or ß) is demonstrated for the DPN-linked liver dehydrogenase which oxidizes uridine diphosphoglucose to uridine diphosphoglucuronic acid.

No abstract

Recently, several efforts to make the college chemistry laboratory a challenging problemoriented exercise have been reported (1-3). A somewhat similar attempt at Georgia State University has produced an integrated problem-based nine quarter sequence covering the first three years. Since a large number of the students passing through the first four quarters have interests associated with biological systems, a problem related to the biochemistry area was sought for one of the early quarters.Much of the free energy needed to drive biological processes is obtained by the hydrolysis of energy-rich phosphate ester derivatives found inside living cells. I n order to gain a better understanding of this hydrolysis process numerous studies (4-6) on simple phosphate (7) W a m~, A,, H m n~~n . P., AND SMITH. E. L.. "Principles of Biochemis try." MoGraw-Hill (4th sd.), 1968. Chap. 11. (8) Lownr, 0. H., AND LOPEZ.