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B L Horecker

Publications and source records attributed to B L Horecker.

At least 91 records · Page 5Linked to original sources
PubMed1982

Synthesis of thymosin beta 4 by peritoneal macrophages and adherent spleen cells.

Thymosin beta 4, previously identified as a component of thymosin fraction 5 isolated from calf thymus, is synthesized by peritoneal macrophages derived from rats or mice, including cells from nu/nu mice. Identification of thymosin beta 4 containing [35S]methionine was based on its retention time in reverse-phase HPLC and the recovery of radioactivity in peptides generated by mild acid hydrolysis or by digestion with trypsin. Thymosin beta 4 is also synthesized by rat and mouse spleen cells, and evidence is presented for its release from these cells.

Animals↗
PubMed1982

Characterization of the inactive form of fructose-1,6-bisphosphate aldolase isolated from livers of fasted rabbits.

The accumulation of an inactive, immunologically crossreactive form of fructose-1,6-bisphosphate aldolase (EC 3.1.3.11) in livers of fasted rabbits has now been related to limited proteolysis at the COOH terminus. The extent of modification of this region of the molecule, determined by analysis of tyrosine residues in the peptides released by digestion with subtilisin, agrees with the observed decrease in the specific activity of the enzyme purified from livers of fasted rabbits. The following evidence supports the conclusion that the modified form is produced in vivo and not during the isolation of the enzyme from the liver homogenates: (i) liver homogenates prepared in isotonic sucrose contained negligible amounts of soluble lysosomal proteinases; (ii) the decreased aldolase activity after fasting was observed in the homogenates and no change in aldolase activity occurred when the homogenates were incubated for 2 hr at 37 degrees C; (iii) the modified enzyme was also isolated from the livers of fasted rabbits when leupeptin was injected intraportally before the animals were sacrificed or when the inhibitor was added to the homogenization solution. On the other hand, homogenization of livers in hypotonic medium resulted in release of lysosomal proteinases and also in decreases in catalytic activity and COOH-terminal modification of liver aldolase, similar to those observed in livers from fasted rabbits. We attribute the changes in activity and structure of aldolase isolated from livers of fasted rabbits to the action in vivo of cathepsin M.

Animals↗
PubMed1982

Thymosins beta 8 and beta 9: two new peptides isolated from calf thymus homologous to thymosin beta 4.

Two new peptides, designated thymosin beta 8 and thymosin beta 9, respectively, have been isolated and their amino acid sequences established. Thymosin beta 8, isolated from calf thymus fraction 5, has a mass of 4518 daltons and contains 39 amino acid residues, of which 31 are identical to the corresponding amino acid residues in thymosin beta 4 isolated from the same source. The NH2 terminus of thymosin beta 8 is acetylalanine, compared with acetylserine in thymosin beta 4. Thymosin beta 9, isolated from fresh-frozen calf thymus by a procedure that minimizes proteolysis, is identical to thymosin beta 8 except for the presence of an additional dipeptide, -Ala-LysOH, at the COOH terminus. It has a mass of 4717 daltons and 32 of its 41 amino acids are identical to those of thymosin beta 4. The similarity in structures of thymosin beta 4 and thymosin beta 9 suggests that they may have related functions.

Animals↗
PubMed1982

Thymosin beta 4: a ubiquitous peptide in rat and mouse tissues.

Thymosin beta 4, recently isolated from calf thymus, is present in a number of rat and mouse tissues, including spleen, thymus, brain, lung, liver, and heart muscle. High concentrations are found in peritoneal macrophages, suggesting that its occurrence in other tissues may be related to the presence of macrophages or macrophage-like cells in these tissues. The conclusion that "thymosin" beta 4 does not originate solely in the thymus gland is supported by the high concentrations found in tissues of athymic (nu/nu) mice.

Animals↗
PubMed1982

Limited proteolysis of liver aldolase and fructose 1,6-bisphosphatase by lysosomal proteinases: effect on complex formation.

Cathepsin M, which catalyzes inactivation of both rabbit liver fructose-1,6-bisphosphate aldolase (EC 4.1.2.13) and rabbit liver fructose 1,6-bisphosphatase (Fru-P2ase; EC 3.1.3.11), has been characterized as a peptidyl peptidase. Modification of the COOH terminus of aldolase by cathepsin M or by Fru-P2ase converting enzyme 2 abolishes its ability to bind to phosphocellulose P11 and to form the complex with Fru-P2ase. On the other hand, modification of the COOH terminus of Fru-P2ase does not affect its interaction with aldolase. This property is lost, however, when Fru-P2ase is modified in the NH2-terminal region by the converting enzyme or by subtilisin. The results suggest that interaction of aldolase and Fru-P2ase may involve the exposed COOH-terminal region of the former and an exposed proteinase-sensitive region located between residues 57 and 67 of the latter.

Amino Acids↗