. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ATP-ASE OF SQUID MUSCLE 115 TABLE I The ATPase activity of fractions isolated from squid mantle muscle Fraction Qp Percentage activity Percentage nitrogen Whole homogenate 1140 Water-sol, ext. (Si) 54 Residue after KC1 ext. 1335 KC1 extract (MS) 1558 ble material contains most of the mantle ATPase activity (Table I). It was from the MS fractions that myosin was precipitated by dilution with 6 volumes of distilled water. In Figure 1 may be seen the effect of magnesium, manganese, or calc
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ATP-ASE OF SQUID MUSCLE 115 TABLE I The ATPase activity of fractions isolated from squid mantle muscle Fraction Qp Percentage activity Percentage nitrogen Whole homogenate 1140 Water-sol, ext. (Si) 54 Residue after KC1 ext. 1335 KC1 extract (MS) 1558 ble material contains most of the mantle ATPase activity (Table I). It was from the MS fractions that myosin was precipitated by dilution with 6 volumes of distilled water. In Figure 1 may be seen the effect of magnesium, manganese, or calcium ions on the ATPase activity of twice-precipitated myosin. Only calcium activates the enzyme to any extent, activating optimally at a concentration of M CaCL both at pH , as is illustrated, or at pH Manganese activates slightly while magnesium is without effect. ATPase activity in the presence of M CaCl2 was found to be optimal at M KC1 but other concentrations of KC1, up to M, were only slightly less effective. The curve illustrating the relationship between myosin-ATPase activity and pH is shown in Figure 2. A definite optimum exists in the region of pH with 2000 • 1500 • 1000 • 500. ION CONCENTRATION (M) FIGURE 1. The effect of different concentrations of calcium, magnesium, or manganese on the ATPase activity of twice-precipitated squid myosin. Activity was measured in M histidine buffer (pH ), M KG, M ATP, and the ions as indicated: CaCl2, • MnClo, e; and MgCl2, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woo
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