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Biomedical subjects

J Jeffery

Publications and source records attributed to J Jeffery.

At least 91 records · Page 5Linked to original sources
PubMed1983

Enzyme relationships in a sorbitol pathway that bypasses glycolysis and pentose phosphates in glucose metabolism.

A pathway from glucose via sorbitol bypasses the control points of hexokinase and phosphofructokinase in glucose metabolism. It also may produce glycerol, linking the bypass to lipid synthesis. Utilization of this bypass is favored by a plentiful supply of glucose--hence, conditions under which glycolysis also is active. The bypass further involves oxidation of NADPH, so the pentose phosphate pathway and the bypass are mutually facilitative. Possible consequences in different organs under normal and pathological, especially diabetic, conditions are detailed. Enzymes with related structures (for example, sorbitol dehydrogenase and alcohol dehydrogenase, and possibly, aldehyde reductase and aldose reductase, respectively) are linked functionally by this scheme. Some enzymes of the bypass also feature in glycolysis (aldolase and alcohol dehydrogenase), and these enzymes, with the reductases involved, are proteins known to occur in different classes or multiple isozyme forms. Two of the enzymes (aldolase and alcohol dehydrogenase) both involve classes with and without a catalytic metal (zinc). The existence of parallel pathways and the occurrence of similar enzymic steps in one pathway may help to explain the abundance and multiplicity of enzymes such as reductases, aldolases, and alcohol dehydrogenases.

Alcoholism↗
PubMed1982

The primary prostaglandin-inactivating enzyme of human placenta is a dimeric short-chain dehydrogenase.

The native form of NAD-dependent 15-hydroxyprostaglandin dehydrogenase of human placenta has a mol. wt. of about 50 000, while the subunit mol. wt. is around 28 000, suggesting a dimeric quaternary structure. These properties, the amino acid composition, insensitivity to EDTA, and inhibition patterns show general similarities to other short-chain dehydrogenases. Several hormones tested did not influence the activity of 15-hydroxyprostaglandin dehydrogenase, but an unusual activation by two anti-depressant drugs was found and may relate to the existence of a natural regulatory factor.

Amino Acids↗
PubMed1981

Alcohol and polyol dehydrogenases are both divided into two protein types, and structural properties cross-relate the different enzyme activities within each type.

Sorbitol dehydrogenase from sheep liver shows similarities to mammalian and yeast alcohol dehydrogenases. Comparisons based on peptides from segments of sorbitol dehydrogenase reveal that homologous regions with 38% identity include two ligands to the active site zinc atom in liver alcohol dehydrogenase, as well as further important residues. Similarities in in other regions are less extensive, exactly as they are between different alcohol dehydrogenases. In all aspects, sorbitol dehydrogenase appears as a typical member of the alcohol dehydrogenase family. On the other hand, alcohol dehydrogenase from Drosophila, which has a shorter subunit, is not closely related to either of these enzymes, except for a region that probably corresponds to the first part of the coenzyme binding domain in many dehydrogenases. Instead, Drosophila alcohol dehydrogenase in its supposed catalytic region shows similarities toward Klebsiella ribitol dehydrogenase, which also has a small subunit. It may be concluded that both alcohol and polyol dehydrogenases show two types of protein subunit, reflecting an early subdivision of polypeptide types into "long" and "short" subunits rather than into different enzymatic specificities or quaternary structures. The relationships explain known properties of all these enzymes and provide insight into functional mechanisms and evolutionary interpretations.

Alcohol Oxidoreductases↗
PubMed1981

Properties of sorbitol dehydrogenase and characterization of a reactive cysteine residue reveal unexpected similarities to alcohol dehydrogenases.

Sorbitol dehydrogenase was characterized as a homogeneous protein on affinity chromatography and ion-exchange chromatography. Tests of stability, sensitivity to inhibitors, and protection by coenzyme suggest that the enzyme has essential cysteine, metal, and probably histidine. The native enzyme has a molecular weight around 140 000 and a subunit around 35 000--40 000, suggesting a tetrameric quaternary structure. Subunits are highly similar if not identical as judged by characterization of one unique 45-residue sequence containing a single reactive cysteine residue. Properties resemble those of mammalian and yeast alcohol dehydrogenases, and the sequence determined for the region around the reactive cysteine residue is homologous to that around one of the zinc-liganding cysteine residues at the active site of horse liver alcohol dehydrogenase. Sorbitol dehydrogenase thus reveals an unexpected relationship to alcohol dehydrogenases, from which ancestral connections and functional mechanisms in this group of enzymes may be further elucidated.

Alcohol Oxidoreductases↗
PubMed1981

Renal transplant uptake of technetium-99m sulfur colloid in various time periods after transplantation.

The uptake of technetium-99m sulfur colloid (TSC) by transplanted kidneys undergoing rejection has been described. In this retrospective study, the value of TSC uptake in diagnosing renal rejection was studied in different time intervals after renal transplantation. Within 14 days after transplantation, increasing uptake was seen in 88% of 26 rejection episodes. In patients with acute tubular necrosis, 42% of their studies showed TSC uptake. TSC did not predict rejection within the three days prior to rejection. Sensitivity, specificity and accuracy of 128 TSC studies were compared at different thresholds of TSC uptake; at best, accuracy was only 76%. In later time intervals, a much smaller percentage of patients had increasing uptake with rejection; this tendency was to remain unchanged. Many non-rejection studies showed some TSC uptake. In chronic rejection, persistently marked uptake dominated prior to one year after transplantation, but not beyond this. Thus, within 14 days after transplantation, TSC uptake may support the diagnosis of rejection. Thereafter its value becomes greatly limited.

Evaluation Studies as Topic↗
PubMed1980

The specificity of dehydrogenases.

The specificity of dehydrogenases for coenzyme (and coenzyme analogues), and substrate (and substrate analogues) is discussed in relation to structure, function, and evolution. Examples concern compounds that have very different structures, reactions that play widely differing roles in the life of the organism, and organisms of greatly differing types. The examples illustrate general points of interest and importance.

Alcohol Oxidoreductases↗