THE DISCOVERY OF PHOSPHAGEN AND EARLY IDEAS OF ITS FUNCTION

In 1927 P. Eggleton & G. P. Eggleton (1), and independently Fiske & Subbarow (2), reported the existence in muscle extracts of a phosphorus compound, very labile especially in acid solution; the figures for inorganic P content of muscle found by earlier workers, using methods involving acid treatment of the extracts, were therefore open to grave doubt.

Eggleton & Eggleton, using the Briggs method (1), in which the colour due to reduced phosphomolybdate is allowed to develop during 30 min in acid solution, found that the increase in colour during this time with inorganic phosphate solutions was only some 5 %; but with extracts from resting frog's muscle the increase was several 100%. They proposed the name ‘phosphagen’ for the labile substance. The value for the true inorganic P of resting muscle, found by extrapolation back to zero time when the rate of colour development was followed, amounted to about 25 mg/100 g muscle; the phosphagen P content to about 60 mg/100 g. Estimations made in neutral or slightly alkaline solution (as in the Bell-Doisy (1) method or by precipitation with magnesia mixture) gave results approximating to the extrapolated values of the Briggs method. In rapidly induced fatigue the true inorganic phosphate increased at the expense of phosphagen P, though not all the phosphate of the disappearing phosphagen was found as inorganic P. In aerobic recovery, phosphagen quickly reappeared at the expense of inorganic P, during a time when little lactic acid removal had yet taken place.