Plasma phosphatase was first determined by Martland (1925) and then by Kay (1930), using glycerophosphate and estimating the inorganic phosphate liberated at 370 C. at a specified pH and in a given time.

OF the several colorimetric methods for the determination of phosphorus which have been described during recent years, probably the Briggs [1922] modification of the Bell and Doisy [1920] method and the method of Fiske and Subbarow [1925] have met with most general favour. Both these methods depend on the reduction of phosphomolybdic acid to give a blue colour, the intensity of which is proportional to the concentration of phosphate. Martland and Robison [1926] proposed a very convenient modification of the Briggs procedure, in which the colour was allowed to develop at an acidity higher than that usually used. Although the total amount of colour was not as great as that developed at lower acidities, a much greater variation in acidity was allowable without any appreciable variation in the amount of colour produced. Consequently, there was no necessity of adjusting the acidity of the test solution, or of adding trichloroacetic acid to the standard to make it similar to the test in acidity and composition. By keeping the sulphuric acid and ammonium molybdate separate they were able to use the same solutions for "free" and for "total" phosphorus. In the latter case the sample was

No abstract

There is much evidence indicating the non-identity of acid phosphatases of different origin. Davies (1934) has shown that the acid phosphatase of the red cell differs from that of spleen in that the former hydrolyses x-glycerophosphate much more readily than the ,-compound, while with the spleen enzyme ,-glycerophosphate is hydrolysed more quickly. Kutscher & Worner (1936) described the irreversible inactivation of the prostatic acid phosphatase by certain narcotics, including alcohols. This was used by Herbert (1944Herbert ( , 1945Herbert ( , 1946 for the identification and determination of the prostatic enzyme in blood serum, whose normal acid phosphatase is hardly affected by ethanol treatment. King, Wood & Delory (1945), on the other hand, found the acid phosphatases of prostate and red cells to be similar in many respects, including easy destruction by ethanol, but formaldehyde and L-tartrate (Abul-Fadl & King, 1947, 1948a sharply distinguish the two enzymes by complete inactivation of the one or the other. In the present investigation the question of the identity of these two acid phosphatases is further dealt with. For this purpose, the rates of hydrolysis of phenyl phosphate by each enzyme at different pH values were determined, together with the relative rates of hydrolysis of aand P-glycerophosphates. This was followed by studies of the effects of organic and inorganic substances belonging to different groups of a possible activating or inhibiting nature. The nature of the enzymes is discussed in the light of these experiments. EXPERIMENTAL Enzyme solutionsNormal fresh human prostate glands were decapsulated, cut into fine pieces and ground with sand in a mortar with 5 times their weight of 0 9 % NaCl solution. A few drops of toluene were added and the mixture was left at room temperature to autolyse for 2-3 days. The mixture was then filtered and highly diluted (e.g. 1000-5000 times) before determining its activity.Freshly drawn samples of blood from man, ox, sheep, pig, rabbit, rat and guinea pig were centrifuged, the plasma with the top layer of white cells separated, and the red cells twice washed with 0.9 % NaCl by spinning and decantation.

For the study of alkaline phosphatase systems a non-phosphate-containing buffer is required. The buffers in common use for the alkaline pH range are ammonia, borate, glytine and veronal. Ammonia and borate have a retarding effect on the rate of ,enzymic hydrolysis of phosphoric esters. Glycine activates phosphatase when present in very low concentrations (0 1-1 mm), but in the concentrations used in the buffer system (0-01-01M) it has an undoubted inhibitory effect. Veronal is much better in this respect, but its useful pH range (6-8-9-6) is not sufficiently high to cover the pH optima of the enzyme acting on aromatic phosphoric esters (Delory & King, 1943). To satisfy the criteria of non-inhibition of enzymic action, useful alkaline pH range, simplicity and reasonable stability, a mixture of sodium carbonate with bicarbonate has been investigated. The range covered, 9-2-10