Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Different histochemical identification methods for muscle fibre types have been introduced over the years. Most of them have been based on myosin ATPase activity after different kinds of preincubations, alone or in combination with oxidative enzymes. Comparative studies have shown, however, that the different methods result in nonidentical subgroups of type II fibres. Optical density values of individual fibres after incubation of serial sections for alkali- or copper-preincubated ATPase, NADH-TR, and fibre diameter, combined in two-dimensional plots, have for a long time been used in our laboratory to separate three subgroups of type II fibres. A cluster analysis, based on the data mentioned above, results in three subgroups of type II fibres in rat plantaris muscle. In comparison, earlier studies comparing different histochemical methods and reporting lack of correspondence between them have been based on two subgroups of type II fibres only. It is suggested that part of the lack of correspondence is due to unequal and incomplete separation by the methods used in the comparative studies, and that the three subgroups of type II fibres identified in the cluster analysis are type IIA, IIX and IIB, respectively. The need for a consensus on a common basis for histochemical identification of muscle fibre types is emphasized.
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PMID:How unequivocal is the muscle fibre type concept? 183 5

The effects of Cd2+ on Ca2+-sensitive myosin ATPase activity were examined. In the absence of Ca2+, the Ca2+-dependent myosin ATPase activity was enhanced by Cd2+ to the same extent as with Ca2+ at concentrations ranging from 10(-6) to 10(-3) M. At 10(-2) M, however, no activation was observed. Zn2+, Co2+, and Sr2+ also activated the myosin ATPase. Sr2+ and Co2+ were less effective. Hg2+, Cr3+, and Cu2+ were essentially inactive. In the presence of below 10(-3) M Ca2+, the increase in the enzyme activity observed on the addition of Cd2+ was in addition to that caused by Ca2+ alone. The ability of metal ions to activate myosin ATPase was compared with that to activate calmodulin-dependent cAMP phosphodiesterase. The activating effects of the metal ions tested were in the order of Ca2+ greater than Cd2+ greater than Zn2+ greater than Co2+ greater than Sr2+ for Ca2+-sensitive myosin ATPase and Ca2+ greater than Cd2+ greater than Sr2+ greater than Zn2+ greater than Hg2+ greater than Co2+ for cAMP phosphodiesterase. Cd2+ activated both enzyme activities most efficiently among the metal ions tested except Ca2+. These results indicate that Cd2+ is able to substitute for Ca2+ in the case of Ca2+ dependent enzymes, regardless of whether or not calmodulin participates in the activating process.
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PMID:Enhancement of Ca2+-sensitive myosin ATPase activity by cadmium. 282 3