The participation of pyridoxal phosphate, carnosine and calcium in the reversal of contraction in muscle fiber systems

Abstract

A relaxing system requiring phosphocreatine as the relaxant may be restored to glycerinated psoas fibers by incubation in a reaction mixture containing pyridoxal phosphate, calcium, carnosine, magnesium, ATP, and sodium maleate at pH 6.5. The capacity to relax, once established, persists after elution in buffer of the diffusible fraction of the reactants. The relaxation by phosphocreatine is reversed by calcium. The restored relaxing system is also subject to relaxation by the dialyzable fraction of the microsomal-free crude muscle extract, but in this case carnosine is not required in the reaction medium.