. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 334 LEONARD NELSON ATP at high enough concentration duplicates this phenomenon' (Curve D, Fig. 3), Mohri (1958) and Nelson (1955) have shown the distinctive magnesium activa- tion of the sperm tail ATP-ase. Evidence from the literature suggests that, with one notable exception cited in Discussion, regardless of enzyme source, inorganic pyrophosphatase activity is generally limited by the magnesium content of the medium. In this respect, the flagellar IPP-ase is not unique. The mutual de- pendence of these enzymes on adequate
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 334 LEONARD NELSON ATP at high enough concentration duplicates this phenomenon' (Curve D, Fig. 3), Mohri (1958) and Nelson (1955) have shown the distinctive magnesium activa- tion of the sperm tail ATP-ase. Evidence from the literature suggests that, with one notable exception cited in Discussion, regardless of enzyme source, inorganic pyrophosphatase activity is generally limited by the magnesium content of the medium. In this respect, the flagellar IPP-ase is not unique. The mutual de- pendence of these enzymes on adequate magnesium ion suggests the validity of the original concept that by chelation, NaPP competes with ATP for the magnesium ions and thereby could exert an inhibitorv influence on the ATP-ase activitv. The .100 .80 .60 .40 -20 -0 >:$. :"o;! •'«-•: •*-• : j •:C: ::ov :.U;.; '<% <; • ,Ml£Sj •O' U' PCMB NEM 2 ATP-ase IPP - ase. 10. 10 10 Inhibitor (M/t) FIGURE 6. Effect of sulfhydryl inhibitors on Mytilus sperm tail enzymes, a. Effect of 10 4 M SH-inhibitor: Ordinate, per cent of control enzyme activity; abscissa, bar 1, control; bar 2, monoiodoacetate; bar 3, N-ethyl maleimide; bar 4, p-chloromercuribenzoate. b. Curves show- ing effect of varying concentrations of N-ethyl maleimide and p-chloromercuribenzoate on sperm tail ATP-ase. Ordinate, per cent of control ATP-ase (no inhibitor) ; abscissa, con- centration of SH-inhibitor (M/liter). Incubation: 10 minutes, ° C. possible significance for sperm motility of this mutual interaction of substrates and enzyme activities will be considered later. When the Lineweaver-Burk (1934) analysis is applied to these unpurified preparations, the Michaelis constants Km, and the maximum velocities Vmnx of the respective enzymatic reactions may be determined graphically (Fig. 5). For the IPP-ase, Kra is X 10~5, and Vmax is y P/mg. protein/10 min., while for ATP-ase Km is X 10'4, and Vmax is 70
Size: 1106px × 2259px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
