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H G Lebherz

Publications and source records attributed to H G Lebherz.

At least 37 records · Page 2Linked to original sources
PubMed1981

Effect of denervation on the levels and rates of synthesis of specific enzymes in "fast-twitch" (breast) muscle fibers of the chicken.

It has been well documented that neural information, or the consequences of it, is required for the full phenotypic expression of different skeletal muscle fiber types. In the present work, we investigate the effect of removal of neural information, via surgical denervation, on the levels and rates of synthesis of several enzyme in mature breast ("fast-twitch") "white" muscle fibers of the chicken. Denervation of these muscles resulted in reductions in the concentrations of several glycolytic enzymes to new steady state levels which were only about 50% of normal, and these decreases in enzyme levels were completed within 2 weeks after severing the nerves. In contrast, denervation for as long as 6 weeks did not have a significant effect on the levels of creatine-P kinase molecules in this muscle type. The decreased level of the skeletal muscle-specific aldolase A4 isoenzyme in denervated breast muscle fibers was associated with a 2- to 3-fold reduction in the relative rate of synthesis of this enzyme following denervation. As expected, denervation had no appreciable effect on the relative rate of synthesis of the muscle-specific MM isoenzyme of creatine-P kinase in this muscle. Our results show that neural information, or the consequences of it, is required to maintain the levels and rates of synthesis of glycolytic enzymes but not of creatine-P kinase in mature fast-twitch muscle fibers. We suggest that denervation results in a partial "dedifferentiation" of these fibers.

Animals↗
PubMed1981

A simple procedure for the isolation of seven abundant muscle enzymes.

The present work describes procedures in which seven major muscle enzymes and serum albumin can be simultaneously isolated from chicken skeletal muscles. The seven enzymes isolated were: phosphorylase, enolase, creatine-P kinase, aldolase, glyceraldehyde-3-P dehydrogenase, phosphoglycerate mutase, and triose-P isomerase. The proteins isolated by these methods were judged to be greater than 97% pure on the basis of electrophoretic analysis in sodium dodecyl sulfate polyacrylamide gels. The procedure is applicable for isolation of the enzymes from large (greater than 100 g) or small (less than 0.5 g) amounts of muscle tissue and the entire procedure can be completed within two days. Particularly useful features of the procedures are: (1) preferential solubilization of the enzymes from myofibrils by extraction of muscle specimens in solutions of different ionic strength; (2) specific precipitation of phosphorylase, creatine-P kinase, and glyceraldehyde 3-Phosphate dehydrogenase from solutions of specified pH and degrees of ammonium sulfate saturation; and (3) an alternate method for isolation of glyceraldehyde-3-P dehydrogenase by specific elution of the enzyme from phosphocellulose columns with ATP. Because of the ease, rapidity, and reproducibility of the procedures, these methods may be useful for the routine isolation of the muscle enzymes in studies on biochemical regulation, as well as for obtaining large quantitites of the enzymes for structural analysis.

Animals↗
PubMed1976

Synthesis of functional aldolase tetramers in a heterologous cell-free system.

The present report describes the complete synthesis of a functional oligomeric enzyme in a heterologous cell-free system. Polysomal RNA from chicken skeletal muscle was used to direct the production of functional aldolase tetramers in wheat germ extracts. The aldolase product was (a) specifically precipitated with monospecific antibodies raised against pure muscle aldolase, (b) had the same subunit molecular weight (40,000) as that of native aldolase (as determined by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate), (c) presumably contained a functional active site since it co-purified with authentic muscle aldolase upon substrate elution from phosphocellulose, and (d) had associated into tetrameric units (Mr=160,000) as shown by centrifugation in sucrose gradients. The present work suggests that, within the cell, post-translational processing of aldolase polypeptide chains is not involved in the formation of functional aldolase tetramers.

Animals↗
PubMed1975

Evidence for the lack of subunit exchange between aldolase tetramers in vivo.

The results of a double isotope experiment using 3H- and 14C-labeled leucine as precursors of protein synthesis demonstrated that the aldolase C to A subunit transition which is associated with chick skeletal muscle development involves the preferential synthesis of different aldolase isoenzymes. This developmental system was used to test for subunit exchange between aldolase tetramers in vivo. In a second double isotope experiment, it was found that the 14C:3H ratios of A and C subunits derived from the same heterotetramer were essentially identical, while the isotope ratios of the same subunit type derived from different isoenzymes were considerably different. Had subunit exchange between the isoenzymes occurred, A subunits of a given heterotetramer would have been expected to have higher isotope ratios than the corresponding C subunits. Therefore, these data suggest that subunit exchange between aldolase tetramers does not occur in vivo, at least not in skeletal muscle to an appreciable extent. The results of the present study suggest that all aldolase tetramers are constructed at the time of the initial assembly of newly synthesized subunits, that is, "new" tetramers would not be generated by subunit exchange between already constructed tetramers. In addition, the present work suggests that the degradation of all four subunits of an aldolase tetramer are coupled inasmuch as the subunits would not be reincorporated into other tetramers. Thus, in contrast to some other proteins, it appears that the subunits of the aldolase tetramer turn over coordinately.

Animals↗
PubMed1975

Synthesis and degradation of fructose diphosphate aldolase isoenzymes in avian brain.

The intraccellular proteins of animal cells are continuously turning over; therefore, the concentration of a given protein is regulated both at the level of protein synthesis and at the level of protein degradation. Studies on the relative rates of turnover of isoenzymes, such as those of aldolase and lactate dehydrogenase, may help to clarify the mechanisms involved in protein turnover. The isoenzymes and subunit types are very similar proteins, and are located within the same intracellular compartments; yet, the concentrations of these proteins are independently regulated. The present paper describes the roles of synthesis and degradation in regulating aldolase isoenzyme concentrations in avian brain...

Animals↗
PubMed1975

Ontogeny and regulation of fructose diphosphate aldolase isoenzymes in "red" and "white" skeletal muscles of the chick.

The quantitative and qualitative changes in fructose-P2 aldolase isoenzyme concentrations during development of "red" (leg) and "white" (breast) skeletal muscles of the chick were investigated. (a) The aldolase C to A subunit transition associated with muscle development is accompanied by large increases in aldolase activity (units/g, wet weight) and in specific catalytic activity (units/mg of protein). The accumulations in both muscle types follow pseudo-first order kinetics with doubling times of 2 to 3 days. The steady state level of aldolase activity in breast muscle (about 150 units/g) is approximately 4-fold higher than that in leg muscle (about 40 units/g). In contrast to leg muscle, the major increase in aldolase activity in breast muscle occurs during postembryonic development. (b) Immunotitration studies demonstrated a direct correlation between increases in enzyme activity and aldolase A subunits during postembryonic muscle development. It was calculated that under steady state conditions, aldolase A4 comprises about 1 percent and 0.26 percent, respectively, of the total wet weight of breast and leg muscle. (c) regulation at the level of protein synthesis in effecting the postembryonic accumulation of aldolase A4 in the muscle types was investigated in short term amino acid incorporation experiments. After a 1-hour pulse with [3H]leucine, aldolase from breast and leg muscle was isolated in a single step by affinity chromatography on phosphocellulose. Incorporation of tritum into aldolase A4 and into soluble or total protein was compared. Between 4 and 38 days after hatching, the rate of aldolase synthesis relative to the synthesis of soluble muscle protein increased about 7- and 3-fold, respectively, in breast and leg muscle. Relative to total protein, incorporation of [3H]leucine into A4 increased about 3-fold in breast muscle, and decreased slightly in leg muscle between 5 and 25 days after hatching. By 3 weeks after hatching, incorporation of [3H]leucine into aldolase A4 relative to incorporation into total protein was about 6-fold higher in breast muscle than it was in leg muscle. The present work, as well as other recent studies, are discussed in relation to the mechanism involved in controlling tissue-specific and stage-specific levels of aldolase isoenzymes in animal cells.

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