The Phosphagens

Storey, K.B. Purification and characterization of arginine kinase from the mantle muscle of the squid, Symplectoteuthis oualaniensis. Role of the phosphagen/phosphagen kinase system in a highly aerobic muscle. Arch. Biochem. Biophys., 179, 518-526 (1977)... 

Muscle and other tissues from both vertebrates and invertebrates usually contain a reserve of high-energy phosphate in the form of phosphagens. The phosphagens are all guanidines and they react reversibly with ATP ... 

It is therefore reasonable to suppose that the phosphagens, as distinct from inorganic PolyPs, arose in the course of evolution subsequent to ATP. The function of detoxification of orthophosphate has in most cases, however, evidently ceased to be necessary as a result of evolutionary development in the higher organisms of a very delicately balanced metabolism and of mechanisms for its precise control. In many cases, the need of elimination of Pi surplus in a form, which is non-toxic to the cell, has again appeared in certain tissues of the higher organisms. 

The main disadvantage with the method is that there is poor control over the number of PS arms linked to the phosphagene ring. It was observed that the number of arms decreased upon increasing molecular weight of the PS arms. This problem leads to the formation of stars with a broad distribution in the number of arms and thus to ill-defined structures. 

No amino acid of the D-series has been found in an active cell constituent of any creature higher on the evolutionary scale than the earthworm (Lumbricus terrestris), which contains the phosphagen lombricine (0-phosphodiester of guanidinoethanol and D-serine) (Ennor et aL, 1960). 

Arg increases spermatogenesis. Various natural products contain the amino acid, e.g. octopine and the phosphagen, arginine phosphate. Arg was first isolated from lupin seedlings in 1886 by Schulze and Steiger. 

The phosphagen is regenerated again at a later stage in the contraction process. 

In the resting muscle, at least 95 per cent, of the creatine is in the bound form of creatine phosphagen, and is maintained at this level by the plasma creatine, which is in equilibrium with the free creatine of the muscle. Creatine is continually being synthesised in accordance with the phosphagen requirements of the muscular and possibly other systems, the surplus being excreted as creatinine. 

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