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Biomedical subjects

B L Horecker

Publications and source records attributed to B L Horecker.

At least 163 records · Page 9Linked to original sources
PubMed1973

Changes in rabbit-liver lysosomes and fructose 1,6-bisphosphatase induced by cold and fasting.

Exposure of rabbits to cold or fasting results in marked increases in the number and size of liver lysosomes, associated with increases in the total and "free" proteolytic activity. Changes in lysosomal morphology also indicate increased activity and fragility. These effects of cold and fasting are correlated with decreases in the levels of liver fructose bisphosphatase (EC 3.1.3.11) activity and changes in the molecular properties of the purified enzyme, including the loss of a small peptide containing the only tryptophan residue in the peptide chain.

Animals↗
PubMed1973

Fructose 1,6-bisphosphatase: the role of lysosomal enzymes in the modification of catalytic and structural properties.

Seasonal variations in the properties of rabbit-liver fructose 1,6-bisphosphatase have now been linked to corresponding changes in the levels of proteolytic activity in the liver extracts. Incubation of native fructose 1,6-bisphosphatase with purified liver lysosomes causes a 3-fold increase in catalytic activity at pH 9.2, with a smaller, and variable, decrease in activity tested at pH 7.5. These changes in catalytic properties are accompanied by the appearance of a smaller subunit, as was previously reported for the enzyme treated with subtilisin. AMP, a negative modulator of fructose bisphosphatase activity, protects against this action of lysosomes. This proteolytic modification of fructose bisphosphatase by lysosomal enzymes may play a role in the modulation of gluconeogenesis.

Animals↗
PubMed1973

Conversion of neutral to alkaline liver fructose 1,6-bisphosphatase: changes in molecular properties of the enzyme.

Removal of the NH(2)-terminal region of fructose 1,6-bisphosphatase from rabbit liver by digestion with subtillisin, or changes in conformation in this region of the protein produced by exposure to low concentrations of urea, result in similar changes in catalytic and allosteric properties of the enzyme. These changes include shift of the pH optimum to more alkaline pH, and loss of sensitivity to inhibition by AMP. The conformation changes are monitored by changes in the fluorescence of the single tryptophan residue, which is located near the NH(2)-terminus. Thus, the tryptophan-containing peptide appears to determine the functional properties of the native enzyme.

Adenosine Monophosphate↗