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T A Koerner

Publications and source records attributed to T A Koerner.

44 records · Page 3Linked to original sources
PubMed1976

The fructose 6-phosphate site of phosphofructokinase. Epimeric specificity.

The epimeric specificity of the catalytic site of rabbit muscle phosphofructokinase was investigated by testing three ketose phosphates as alternate substrates. These (and their epimeric carbons) included: D-psicose-6-P (C-3), D-tagatose-6-P (C-4), and L-sorbose-6-P (C-5). The Michaelis constants (and relative maximal velocities) were: 3.0 mM (45%), 0.054 mM (104%), and 11 mM (15%), respectively. Under the same conditions, D-fructose-6-P had a Km of 0.043 mM and an arbitrary Vmax of 100%. The low affinity of the enzyme for D-psicose-6-P indicates that the L configuration at C-3 is required for effective binding, a specificity similar to several other fructose-metabolizing enzymes. The D configuration at C-5 is also important for tight binding and the proper orientation of the phosphate group of the substrate. The kinetic constants of D-tagatose-6-P were identical with those of D-fructose-6-P, within experimental error. Thus, the configuration at C-4 is not essential for activity; an indication that D-tagatose may be utilized in mammalian tissues. A novel method for the synthesis of D-psicose-6-P and an improved procedure for the synthesis of D-tagatose-6-P are described. All products and intermediates were characterized unequivocally by chemical and physical methods.

Animals↗
PubMedDate not supplied

The effect of storage on the ganglioside content of human platelets.

Gangliosides are glycolipids which contain sialic acid and are found in the membranes of mammalian cells. By analogy with recent studies of other cells, it is possible that gangliosides play a role in the membrane functions and in vivo survival of platelets. In order to determine if ganglioside destruction plays a role in the storage-induced loss of platelet viability and function (storage lesion), the ganglioside content of platelets was measured after 24 and 96 hours of storage. Samples were taken from platelet concentrates that were stored either on a flat-bed shaker (n = 6) or on a circular rotator (n = 6). Total ganglioside content was determined colorimetrically from the total lipid extracts of purified platelet pellets using the Svennerholm resorcinol method. Ganglioside GM3 content was determined by Folch partitioning, high performance thin-layer chromatography, and densitometric scanning. Ganglioside content, measured as microgram of lipid-bound sialic acid per 10(10) platelets, was significantly decreased (p less than 0.005) between 24 and 96 hours of storage, whether measured as total or GM3 ganglioside. The mean values +/- SEM at 24 and 96 hours of storage were 9.4 +/- 0.6 and 6.7 +/- 0.6, respectively (n = 12 for each). These data indicate that storage causes irreversible loss of membrane ganglioside, which may be detrimental to the function and in vivo survival of platelets.

Blood Platelets↗