muscle enzymes


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muscle enzymes

the table lists some of the most often-mentioned enzymes present in skeletal muscle, with their locations and functions. Apart from actomyosin and myosin ATPases which are associated with the contractile mechanism, they are by no means specific to muscle, being present and highly active also in other tissues. See also Krebs cycle, muscle fibre types.
Table 1: Muscle enzymes
Name SiteCatalyses…
Actomyosin ATPase (amATPase) myosin head groups hydrolysis (Mg-dependent and triggered by rise in [Ca2+]) of terminal phosphate group of ATP when head-group is in interaction with actin, releasing energy that powers force- generation. (Compare myosin ATPase)
Creatine kinase (CK) cytoplasm transfer of phosphate group from creatine phosphate to ADP, producing ATP and creatine. Isoenzymes can be distinguished in blood when either skeletal or cardiac muscle has been damaged.
Hexokinase (HK) cytoplasm 'capture' of glucose after uptake from the blood, by conversion to the impermeant glucose 6-phosphate, in type 1 muscle fibres, which utilize glucose directly.
Lactate dehydrogenase (LDH) cytoplasm reduction of pyruvate to lactate when oxygen tension is low, and the converse when it is high. Isoenzymes can be distinguished in blood when either skeletal or cardiac muscle has been damaged.
Myosin ATPase (mATPase) myosin head groups hydrolysis (Ca2+ dependent, Mg2+ independent) of terminal phosphate group of ATP by head group alone, not interacting with actin (so not contraction-producing: cf actomyosin ATPase). Basic histochemical marker for fast vs. slow fibres.
Phosphofructokinase (PFK) cytoplasm conversion of fructose 6-phosphate to fructose 1,6-diphosphate; rate-limiting for glycolysis, and sensitive to very many stimulatory and inhibitory influences.
Phosphorylase (PPL) cytoplasmremoval of hexose units, one at a time, from glycogen, to form glucose 1-phosphate: rate-limiting enzyme of, and histochemical marker for, glycogenolysis.
Pyruvate dehydrogenase (PDH) mitochondrial envelope oxidative decarboxylation of pyruvate (from cytoplasm) to form acetyl CoA, which thence feeds into tricarboxylic acid (Krebs) cycle
Sarcoplasmic reticulum ATPase (srATPase) SR membrane pumping of [Ca2+] back into SR after its electrically stimulated release
Succinate dehydrogenase (SDH) mitochondrial inner membrane oxidation of succinate to fumarate, in tricarboxylic acid (Krebs) cycle. Histochemical marker for aerobic capacity.
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Therefore, we performed a historical cohort study to objectively assess the efficacy of glucocorticoids and riboflavin on late-onset MADD patients and compared the changes in muscle strength and muscle enzymes between these two therapies.
Four of the 5 criteria are related to the muscle disease as follows: progressive proximal symmetrical weakness, elevated levels of muscle enzymes, an abnormal finding on electromyography, and an abnormal finding on muscle biopsy.
As reported in the text, patient anamnesis and clinical examination excluded each systemic diseases, including cardiovascular, thyroid and neoplastic pathologies, that can cause an increase in circulating muscle enzyme levels.
Despite the association of black cohosh with high muscle enzymes serum levels, the authors point out that none of the biological effects demonstrated for the main components of black cohosh can explain the myopathic effect described in the report.
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Newmarket trainer Pat Gilligan explained: "He's had a long-term problem with muscle enzymes, which ties him up with cramping.
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Although some children with suspect or probable SARS developed elevated liver and/or muscle enzymes, neutropenia, or lymphocytopenia, the pattern didn't distinguish them from the children with other-cause illnesses.
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Two other muscle enzymes, which might help in the burning of fat during exercise, were more active in the older athletes, which may be another advantage.