© 1971 by The Society for Integrative and Comparative Biology
Contractile Proteins of a Benthic Fish.I. Effects of Temperature and Pressure on Myosin ATPase.
Department of Medicine and Program in Biophysics, State University of New York Downstate Medical Center Brooklyn, New York 11203
Department of Physiology, University of California Los Angeles, California 90024
SYNOPSIS. Studies are described on the adenosine triphosphatase (ATPase) properties of myosin isolated from skeletal muscle of Coryphaenoides, a benthic fish captured at 2,200 meters depth. Ca2+-ATPase and EDTA-ATPase of Coryphaenoides myosin show the same pH dependence as ATPase of mammalian myosin; however, rates of ATP hydrolysis by Coryphaenoides myosin are only 5–10% of rates of ATP hydrolysis by rabbit skeletal myosin. Coryphaenoides myosin ATPase shows a decrease from Q10 of 2.0 at 25°C to Q10 of 1.4 a t 2°C, and undergoes irreversible denaturation at temperatures above 25°C. At pH 6.8 to pH 8.5, Coryphaenoides myosin ATPase undergoes activation by pressure at 25°C, but at 2°C shows negligible effect of pressure at values below 3,000 psi. The kinetic data on Ca2+-ATPase indicate values of 11 kcal/mole for 
H
, –7.5 kcal/mole for TS, and –5.7 cc/mole for V at 25°C, pH 7.6. Comparable data at 2°C indicate values of 5 kcal/mole for H. –13 kcal/mole for TS, and negligible V. According to the results of 25°C, Ca2+-activatkm of myosin-ATP may involve disruption of four or five hydrophobic or polar groups, presumably due to an "opening-up" of the myosin molecule at or near the site for ATP binding. It would also appear that Coryphaenoides myosin has undergone an adaptive change in the enzyme mechanism for ATPase such that the rate of ATP hydrolysis is relatively insensitive to pressure and temperature under conditions encountered by the living fish.