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Biol Bull 108: 113-119. (February 1955)
© 1955 Marine Biological Laboratory
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ADENOSINETRIPHOSPHATASE ACTIVITY OF SQUID MANTLE MUSCLE (LOLIGO PEALII)

GEORGE W. DE VILLAFRANCA 1

1 Department of Zoology, Smith College, Northampton, Mass.

1. It is highly probable that the mantle muscle of the squid, Loligo pealii, has only one ATPase, associated with the myosin-like proteins extracted with 0.5 M KCl. It lacks a water-soluble, or particulate-bound, ATPase comparable to that found in vertebrate and certain insect muscle.

2. The extremely labile myosin-ATPase is activated almost 10-fold by 0.01 M CaCl2 and almost 4-fold by 0.001 M MnCl2. Magnesium is without effect. The pH optimum for this enzyme is approximately pH 5.9. A true ATPase, being specific for the terminal phosphate of ATP, it also hydrolyzes ITP at a somewhat reduced rate. An average Michaelis-Menten constant of 3.05 x 10-4 and a Qp as high as 2000, comparable to mammalian myosin-ATPase and much higher than other marine invertebrates, have been obtained.






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Copyright © 1955 by the Marine Biological Laboratory.