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Biomedical subjects

B L Horecker

Publications and source records attributed to B L Horecker.

At least 109 records · Page 6Linked to original sources
PubMed1981

Purification of thymus mRNA coding for a 16,000-dalton polypeptide containing the thymosin alpha 1 sequence.

A mRNA fraction purified by preparative polyacrylamide disc gel electrophoresis from calf thymus polysomes codes for a polypeptide(s) having a mass of 16,000-17,000 daltons. This polypeptide contains amino acid sequences corresponding to residues 11-18 and 19-25 of thymosin alpha 1. The yield of the octapeptide indicates that the 16,000-dalton peptide is the major product formed in the cell-free synthesis system containing the purified mRNA.

Animals↗
PubMed1981

Changes during fasting in the activity of a specific lysosomal proteinase, fructose-1,6-bisphosphatase converting enzyme.

Three lysosomal proteinases capable of catalyzing a limited modification of the gluconeogenic enzyme fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) have been purified from extracts of rabbit liver lysosomes. These have been designated "converting enzymes I, II, and III," respectively, based on the order of their elution from Ultrogel AcA34. The predominant form in lysosomes from livers of fed rabbits is converting enzyme III which has been identified as a mixture of cathepsins B and L. Fasting induces a 4- to 5-fold increase in the activity of converting enzyme II; in the livers of 96-hr-fasted rabbits, this form accounts for more than 70% of the total converting enzyme activity. The increase is largely in that fraction of converting enzyme II associated with lysosomal membranes; this increase is also seen in the activity expressed by intact lysosomes. The activity of intact lysosomes is not due to their increased fragility because other lysosomal enzyme activities remain latent. The effect of fasting on the activity of converting enzyme II is selective and greatly exceeds the 2-fold increase observed for other lysosomal enzymes.

Animals↗
PubMed1980

Evidence for formation of a rabbit liver aldolase--rabbit liver fructose-1,6-bisphosphatase complex.

The ability of rabbit liver aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphatate-lyase, EC 4.1.2.13) and rabbit liver fructose-1,6-bisphosphatase (Fru-P2ase; D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) to partition into the gel phase of Ultrogel AcA 34 is decreased in a mixture of the two enzymes. Titration experiments indicate that a 1:1 complex is formed. The value for the distribution coefficient of the complex corresponds to a molecular mass of 300,000 daltons, the value expected for a dimer containing one mole of each enzyme protein. Complex formation was not observed when either liver enzyme was replaced by the corresponding isozyme from rabbit muscle. The susceptibility of liver Fru-P2ase to limited proteolysis by subtilisin was reduced in the presence of liver aldolase, but not when the latter was replaced by muscle aldolase, suggesting that the conformation of Fru-P2ase is altered in the complex. Limited proteolysis of liver aldolase abolishes its ability both to form the heterodimer and to protect Fru-P2ase from modification by subtilisin.

Allosteric Regulation↗
PubMed1979

Changes in activity of fructose-1,6-bisphosphate aldolase in livers of fasted rabbits and accumulation of crossreacting immune material.

The activity of fructose-1,6-bisphosphate aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) in livers of fasted rabbits decreases to less than one-half the value found in livers of fed rabbits. However, the concentration of aldolase protein in the liver extracts, measured with a specific antibody, remains unchanged. More than twice as much antibody is required to neutralize the aldolase activity in liver extracts from fasted compared with fed rabbits. The results suggest that modification of liver aldolase occurs during fasting, resulting in loss of catalytic activity without loss of immunoreactivity.

Animals↗