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Biomedical subjects

C J Masters

Publications and source records attributed to C J Masters.

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

The reversible binding of glycolytic enzymes in ovine skeletal muscle in response to tetanic stimulation.

The extent of binding of glycolytic enzymes to the particulate fraction of homogenates was measured in sheep hind muscles after electrical stimulation. As compared to the control muscles, stimulation led to significant increases in the amount of phosphofructokinase, aldolase and glyceraldehyde-3-phosphate dehydrogenase bound to the particulate fraction. The binding of other glycolytic enzymes was not significantly altered. A servey of different hind limb muscles at variable rates of stimulation revealed that each muscle exhibited its own characteristic response pattern in terms of the level of increased enzyme binding. Generally, an increased stimulation rate led to greater enzyme adsorption. The increase in enzyme binding was rapidly reversible for it was shown that the amount of enzyme bound quickly returned to control values when the muscles were allowed to recover in the live anaesthetised animal following cessation of stimulation. Those muscles which exhibited increased enzyme binding were characterised by a marked loss of glycogen and accumulation of lactate suggesting that accelerated glycolytic flux was a necessary condition for the observation of increased enzyme binding. In support of this, enzyme adsorption was observed to the greatest on stimulation of ischemic muscles, whereas in trained muscles, or muscles with depleted glycogen stores induced by prior adrenalin treatment, the increased enzyme binding response was greatly diminished. It is concluded that the variable binding of key glycolytic enzymes has a role to play in the regulation of glycolytic behaviour in skeletal muscle.

Animals↗
PubMed1981

Binding of aldolase to actin-containing filaments. Quantitative reappraisal of the interactions.

Previously reported results of equilibrium-partition experiments on the interaction of aldolase with actin-containing filaments [Walsh, Winzor, Clarke, Masters & Morton (1980) Biochem. J. 186, 89-98] have been subjected to a more rigorous theoretical analysis involving consideration of the consequences of cross-linking interactions between enzyme and filament. The experimental results obtained with F-actin-tropomyosin are best described by a model with one binding site per heptameric repeat unit of filament and a value of 39000 M-1 for the site binding constant, k. Similar analyses of the influence of Ca2+ on aldolase binding to F-actin--tropomyosin--troponin substantiate the existence of two equivalent binding sites (k = 14900 M-1) for the enzyme on each repeat unit of the thin filament. The Ca2+-sensitivity of this interaction reflects either a decrease in the strength of aldolase binding to these two sites (k = 8200 M-1) or the elimination of one site.

Actins↗
PubMed1981

Interactions between soluble enzymes and subcellular structure.

Soluble enzymes contribute significantly to the metabolic capabilities of living organisms, but it is becoming increasingly clear that the activities of these enzymes are significantly modified by their interactions with structural components of the cells, and that these interactions may make important contributions to metabolic regulation. In the past, specification of these interactions has been limited by the availability of suitable experimental techniques, but this deficiency is now being rectified and our understanding of these processes if advancing rapidly. Research in this area is moving into a second phase, with the emphasis no longer being focused on demonstrations of the biological reality of these interactions, but directed more towards quantitative aspects of binding, the determination of the characteristics of binding domains, and the theoretical basis of regulatory involvements. All of these aspects are discussed in the present review.

Animals↗
PubMed1980

Binding of aldolase to actin-containing filaments. Evidence of interaction with the regulatory proteins of skeletal muscle.

The interactions of aldolase with regulatory proteins of rabbit skeletal muscle were investigated by moving-boundary electrophoresis. A salt-dependent interaction of troponin, tropomyosin and the tropomyosin-troponin complex with aldolase was detected, the tropomyosin-troponin complex displaying a greater affinity for the enzyme than did either regulatory protein alone. The results indicate that aldolase possesses multiple binding sites (three or more) for these muscle proteins. Quantitative studies of the binding of aldolase to actin-containing filaments showed the interaction to be influenced markedly by the presence of these muscle regulatory proteins on the filaments. In imidazole/HCl buffer, I 0.088, pH 6.8, aldolase binds to F-actin with an affinity constant of 2 x 10(5) M-1 and a stoicheiometry of one tetrameric aldolase molecule per 14 monomeric actin units. Use of F-actin-tropomyosin as adsorbent results in a doubling of the stoicheiometry without significant change in the intrinsic association constant. With F-actin-tropomyosin-troponin a lower binding constant (6 x 10(4) M-1) but even greater stoicheiometry (4:14 actin units) are observed. The presence of Ca2+ (0.1 mM) decreases this stoicheiometry to 3:14 without affecting significantly the magnitude of the intrinsic binding constant.

Actins↗
PubMed1978

The turnover of lactate dehydrogenase in skeletal muscle of the mouse. Influence of fibre type and exercise regimen.

1. The influence of fibre-type and an exercise regimen on the turnover characteristics of proteins in mouse skeletal muscle has been studied. 2. Exercise induced a weight increase in most individual muscles and a decrease in lactate dehydrogenase activity which was more marked in white muscle than red. The coincident decrease in M-subunit activity was more noticeable in fast-twitch muscles than in slow-twitch types. 3. Exercise caused a considerable and consistent increase in the rate of degradation of total soluble proteins in individual muscles, with turnover being higher in muscles with a high red fibre content. 4. The response of lactate dehydrogenase to exercise varied considerably between individual muscles as indicated by the comparative rate constants for synthesis and degradation. In general, degradation was greater in muscle with a high slow-twitch or red fibre content. 5. Overall, a considerable redistribution of protein resources was observed during this physiological perturbation (exercise) with the main emphasis away from the pool of total soluble protein towards the myofibrillar constituents. Highly individualistic responses in relation to rates of synthesis and degradation were observed for the specific protein, lactate dehydrogenase, in the separate muscle of this animal.

Actomyosin↗
PubMed1978

Effect of pregnancy on the turnover of lactate dehydrogenase and its isoenzymes in mouse tissues.

The turnover characteristics of total protein and of lactate dehydrogenase and its isoenzymes have been determined in several tissues of the mouse during the later stages of pregnancy. Whereas most tissues showed markedly decreased rates of both synthesis and degradation of proteins, the incorporation rate in uterus increased. Significant differences in the extent of isotope distribution between total protein and lactate dehydrogenase and its isozymes were also noted. Overall the concept emerges of a pool of body protein which is responsive to the physiological stresses of pregnancy at the level of both tissue and cellular function.

Animals↗
PubMed1978

On the localization of lactate dehydrogenase in the ovaries and reproductive tracts of rats and mice.

The localization of lactate dehydrogenase in the ovaries and reproductive tracts of rats and mice has been studied by a methodology which minimizes loss of this soluble enzyme by diffusion, and allows comment on the subunit composition of the cellular enzyme. The results differ significantly from previous data with conventional methodologies. In particular, the major localization of activity in the present study was identified in interstitial cells, and not the corpora lutea or granulosa cells; and it was noticeable that neither species exhibited massively greater expression of lactate dehydrogenase activity in the oocytes than in adjacent cell types of the reproductive tract. The goblet cells of the Fallopian tube stained intensively for activity of this enzyme. These results have been discussed in relation to the discordant data in the literature, the important role of lactate dehydrogenase in mammalian development, and the evidence for a masking of the activity of this enzyme in oocytes and pre-implantation ova.

Animals↗