A study of the effects of substrate concentration and certain relaxing factors on the magnesium-activated myofibrillar adenosine triphosphatase

Abstract

Marsh (1952) first showed that whereas the apparent rate of hydrolysis of adenosine triphosphate (ATP) by homogenates of fresh rabbit muscle in an isotonic solution of potassium chloride was comparatively low, after centrifuging and removal of the soluble protein extract a considerable increase in the rate of production of inorganic phosphate by the residue occurred when it was resuspended in fresh potassium chloride solution. On the basis of these findings Marsh concluded that there was present in muscle a factor which inhibited adenosine triphosphatase (ATPase) activity, and he further demonstrated that in the presence of this factor ATP caused an increase in the volume of the cell fragments in the suspension. Bendall (1953 a) extended Marsh's findings and was able to bring about the relaxation of glycerated fibres by the application of ATP in the presence of preparations of the Marsh factor. He also confirmed the inhibitory action of the factor on the ATPase activity of homogenized glycerated fibres. Further investigations by Hasselbach & Weber (1953) on the ATPase activity of these preparations showed that at higher concentrations ATP was inhibitory, and in the presence of the Marsh factor the level at which ATP became inhibitory was considerably reduced.It is clear from the investigations mentioned above and those of Bozler & Prince (1953) that, in general, relaxation in muscle models is associated with a low rate of ATP hydrolysis. Magnesium appears to be of special importance in the contraction-relaxation cycle, yet the precise role of this metal is far from clear. Although magnesium is essential for relaxation (Bendall, 1953a), reagents which form complexes with magnesium, namely ethylenediaminetetraacetate (EDTA) (Bozler, 1954;Watanabe, 1955) and inorganic pyrophosphate (Weber, 1951;Bozler, 1951; Bendall, 1953b) also bring about relaxation of glycerated fibres. Bendall (1953b) has commented on the similarity between the relaxing action of the Marsh factor and that of inorganic pyrophosphate, and it is conceivable that one of the properties possessed in common by these substances is the ability to complex with magnesium.Glycerated fibres consist mainly of myofibrils, but studies on the ATPase activity ofthese fibres are not entirely satisfactory, as preparations may be contaminated with sarcoplasmic granules and nuclei which also possess ATPase activity, and with varying amounts of sarcoplasm. Furthermore, precise analysis of such experiments in terms of substrate and activator concentrations at any point in the fibre is difficult because concentration gradients will be produced by the diffusion of ATP to the myofibrils from the outside of the fibre. To throw more light on the enzymic behaviour of the myofibril a study has been made of the ATPase activity of isolated myofibrils, with particular reference to those conditions that bring about the low level of activity which is characteristic of relaxation. It has been shown that at a low ionic strength the marked inhibition of ATPase activity by ATP is de...

Different Adsorption Behavior of Rare Earth and Metallic Ion Complexes on Langmuir Monolayers Probed by Sum-Frequency Generation Spectroscopy

“…As an alignment of water dipoles is made in the direction of the surface normal, it leads to the increase of direction cosine average in the second-order susceptibility in Eq. (2). Apparently, the spectral shape in the CHx region was also changed slightly in high pH; for example, higher peak strength of CH3 fermi resonance than symmetric stretch mode.…”

“…, β , and (2) χ ↔ are the overlapping area of two input beams, input beam pulse width, unit vector in the polarization direction, tensor of the Fresnel factor, SF light angle in the reflection direction, and secondorder susceptibility tensor, respectively. In this equation, (2) χ ↔ is determined by the characteristics of the surface, and is expressed using the second-order hyperpolarizability of the molecule as follows.…”

“…In this equation, (2) χ ↔ is determined by the characteristics of the surface, and is expressed using the second-order hyperpolarizability of the molecule as follows. 2.…”

“…For example, in the cell membrane of a neuron, the K + / Na + pump controls electric potential difference between the inner and the outer cell membrane in order to regulate important cellular functions such as muscle contraction, and neuron function [1]. Mg 2+ makes a complex with ATP which carries chemical energy in the cell [2]. Unlike these well-known simple mono-and divalent cations, metal hydroxides such as Fe(OH) x +3-x are rarely found in living organisms.…”

Golden days of British muscle biochemistry

“…At that time the Perry lab was first to confirm that traces of Ca 2? are critically regulating myofibrillar activity employing the cation chelator glycolcomplexon (Perry and Grey 1956) which was obtained from Gerold Schwarzenbach, Anorganic Chemistry, Swiss Federal Institute of Technology (ETH, Zurich). Glycolcomplexon, later to be known as EGTA, specifically chelates Ca 2?…”