The adenosinetriphosphatase activity of myosin preparations

Historical Perspective: Heat production and chemical change in muscle. Roger C. Woledge

The objective of this article is to provide an historical perspective on a review of "Heat production and chemical change in muscle" written by Roger C. Woledge and published in Progress in Biophysics and Molecular Biology 50 years ago. We first provide a brief but broad summary of the history of muscle chemistry prior to 1971 and then address the central theme of the 1971 review - that of energy balance. Energy balance is a method to establish whether all the energetically significant biochemical reactions accompanying muscle contraction have been identified. Woledge adopted the method to compare the measured enthalpy output (i.e., the sum of the heat output and work output) to that expected from the extent of known biochemical reactions. Prior work had suggested that the observed and expected enthalpy outputs were similar but Woledge proposed that the expected heat had been overestimated and that, hence, there must be an unidentified reaction that accounted for as much as half the heat produced by a contracting muscle. We describe investigations carried out after the review that vindicated that view, ultimately characterising the processes producing the unexplained enthalpy which, in turn, led to identification of the hitherto unknown reaction. Those experiments and a more recent resurrection of the approach using fluorescent probes to monitor ATP turnover have now accounted for the processes that underlie the complex time courses of muscle heat production and ATP turnover during contraction, at least in the classical frog sartorius muscle preparation. However, the few studies performed on mammalian muscles since then have produced results that are difficult to reconcile with the ideas derived from energy balance studies of amphibian and fish muscles, thereby suggesting a new objective for energy balance studies.

A STUDY OF THE ADENOSINE TRIPHOSPHATASE ACTIVITY OF MYOSIN AND ACTOMYOSIN

1. An experimental study was made on the adenosine triphosphatase action of crystalline myosin and actomyosin preparations under different conditions. 2. No enzymatic activity was found in the absence of salts. Activation was given by KCl and CaCl₂, whereas MgCl₂ in the presence of other ions inhibited. 3. The effect of pH is complex. In stabilizing buffers or at low temperature, there are two optima (pH 6.2 to 6.5 and pH 9.2) provided Ca is present. Without Ca only the acid optimum is found. The highest activities are reached in glycine buffer at pH 9.2 in the presence of Ca. 4. The study of the Mg-Ca antagonism revealed that the inhibition due to Mg is fully developed with Mg:Ca ratios less than 1, the inhibition usually exceeding 90 per cent. 5. It is shown that in the muscle the myosin-ATPase is most probably also subjected to the inhibitory action of the Mg ions. 6. From data in the literature it is calculated that the liberation of inorganic phosphate during muscular activity takes place at a rate of at least 0.200 mg. P per mg. myosin per minute. 7. From the results of the present study it is found that the myosin in the muscle can liberate inorganic phosphate from ATP at a rate of at most 0.003 mg. P per mg. myosin per minute. 8. It is concluded therefore that myosin-ATPase cannot be responsible for the liberation of the main part of the phosphate in contracting muscle, and therefore cannot have the rôle in muscular metabolism ascribed to it in recent hypotheses and discussions.

MEASUREMENT OF ANAEROBIC GLYCOLYSIS IN BRAIN AS RELATED TO POLIOMYELITIS

Experiments with mouse brain, homogenates show that the anaerobic glycolysis of such preparations can be increased tenfold by addition of appropriate coenzymes and phosphate esters. The previously reported alterations in anaerobic glycolysis during poliomyelitis, as measured with low activity preparations, are believed to be of doubtful value in so far as the changes may be related to any specific phase of metabolism. In order to obtain this type of information, the experiment usually must be designed specifically to measure the desired factor.

Evidence of active transfer of certain non-electrolytes across the human red cell membrane

1. Permeability of the human erythrocyte to glycerol, as indicated by the course of hemolysis and volume changes, is depressed by Cu⁺⁺, Hg⁺⁺, I₂, p-chloromercuribenzoate, and phlorhizin, without effecting general permeability changes. In so far as tested (Cu⁺⁺, p-ClHgB), these inhibitors delay exit of glycerol from the cell as well as its entry. 2. Permeability to glucose is similarly depressed by I₂ and phlorhizin, and is extremely sensitive to Hg⁺⁺ and p-chloromercuribenzoate, but is not affected by Cu⁺⁺. An extensive series of other enzyme poisons is without effect in either system. 3. The effects of the sulfhydryl inhibitors are prevented or reversed in the presence of glutathione, cysteine, etc. 4. The kinetics of the volume changes in glucose-saline solutions indicates a mechanism for transport of glucose into the cell, regulated by the existing intracellular concentration, rather than by simple diffusion gradients. 5. The intermediation of a sulfhydryl group at the cell surface, probably an enzymatic phosphorylation, is suggested as an essential step in the passage of glycerol, glucose, and other like substances, across the human red cell membrane.

Studies on the rigor resulting from the thawing of frozen frog sartorius muscle

1. The rigor which takes place when completely frozen frog sartorius muscle is thawed ("thaw rigor"), is accompanied by a decrease in length of 70 per cent and a loss in weight of 35 per cent, whether the muscle is frozen in the resting or the exhausted condition, or during isometric tetanus. Muscle tetanized to maximal shortening shows a loss in weight of 25 per cent on thawing. 2. A load of 8 gm. is sufficient to prevent the decrease in length on thawing, but after its removal the muscle will shorten almost to the normal extent. 3. Inhibitors such as azide, cyanide, 2:4 dinitrophenol, p-chloromercuribenzoate, Cu, and hydrogen peroxide, when used for periods not exceeding 1 hour, have little effect on the shortening; although in some cases these poisons render the muscle inexcitable. 4. Muscles poisoned with iodoacetic acid and stimulated to exhaustion, or maintained at fixed length in nitrogen, show little or no shortening on thawing. ATP can produce shortening in the muscles in which it has been prevented. 5. The phenomenon is considered to be due to an in situ synaeresis of the actomyosin of the myofibrils. As a result of the disorganisation of the muscle protoplasm produced by the freezing and subsequent thawing, the ATP, which must be bound or localized in the resting muscle, can act on the myofibril in a similar manner to its in vitro effect on the actomyosin thread.

Recurring views on the structure and function of the cytoskeleton: a 300-year epic

Some unnoticed or seldom remembered precedents of current views on biological motion and its structural bases are briefly outlined, followed by a concise recapitulation of how the present theory has been constructed in the last few decades. It is shown that the evolution of the concept of fibers as main constituents of living matter led to hypothesizing microscopic structures closely resembling microtubules in the 18th century. At the beginning of this period, fibers sliding over each other and driven by interposed moving elements were envisioned as the cause of muscle contraction. In the following century, an account of the mechanism of myofibril contraction visualized longitudinal displacements of myosin-containing submicroscopic rodlets. The existence of fibrils in the protoplasm of non-muscle cells, a subject of long debate in the second half of the 19th century, was virtually discarded as irrelevant or fallacious 100 years ago. The issue resurfaced in the early 1930s as a theoretical notion--the cytosquelette--nearly two decades before intracellular filamentous structures were first observed with electron microscopy. The role originally assumed for such fibrils as signal conductors is nowadays being reappraised, although under new interpretations with a much wider significance including modulation of gene expression, morphogenesis, and even consciousness. Since all of the above ancestral conceptions were eventually abandoned, the corresponding current views are, to a certain extent, recurrent.

Age Changes in Adenine Nucleotides in Flight Muscle of Male House Fly

Under standard conditions of temperature, humidity, and (artificial) diet, loss in flight ability is paralleled by a decline of up to 66(2/3) percent in activity of enzymes dephosphorylating organophosphorous compounds in the thoracic flight muscle. Concomitantly, the content of adenosine triphosphate in the flight muscle increases five times, while the content of adenosine monophosphate correspondingly diminishes.

The enzymic activation of cholic acid by guinea-pig-liver microsomes

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The respiratory and adenosinetriphosphatase activities of skeletal-muscle mitochondria

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