No abstract

THE phosphatase obtained from the bones of growing animals has proved very useful in the study of the chemical composition of phosphoric esters of biochemical interest. By its aid the phosphoric acid groups may be quanti

IN the earlier papers of this series [Robison and Soames, 1924] some account was given of the properties of the phosphatase which is present in ossifying cartilage, bones and teeth, and also in the kidney and intestinal mucosa. In the following we give the results of a more detailed study of some of its properties about which further knowledge was desirable in order to understand the part played by this enzyme and by phosphoric esters in the process of ossification. OPTIMUM PH. It was previously stated that the optimum PH of this enzyme lies on a flat curve between 8-4 and 9-4, the activity being nearly constant between these limits, but falling off rapidly on either side of them. This statement was based on results of 18-hour experiments, but later observations suggested that the flattening of the curve was in part due to the gradual inactivation of the enzyme at the higher PH values and that over short periods of time the activity continues to increase with the alkalinity up to a PH well above 8-4. More exact investigation of the course of hydrolysis has shown that these suppositions are correct. Fig. 1 shows the rate of hydrolysis of glycerophosphoric ester over a period of 5 hours at pH between 7.25 and 9-4. Further measurements, not shown on the chart, were taken at the end of 24, 48 and 166 hours. The PH was determined from time to time by a micro-colorimetric method (capillator) on 002 cc. liquid withdrawn from the reacting mixture. The addition of indicators to the bulk of the liquid was inadmissible on account of the subsequent colorimetric estimations of inorganic phosphate (Briggs). In this experiment the initial rate increased with the alkalinity up to 9 4, the highest PH attempted, but at the end of 24 hours the amount

No abstract

PREVIOUS experiments [Robison, 1923], which demonstrated the presence of a phosphoric esterase in the bones of young animals, failed to detect this enzyme in unossified cartilage. The present work was undertaken to confirm this observation, and to determine whether any correlation could be traced between the appearance of the enzyme and the beginning of the ossification process in the cartilage. Our first experiments were carried out on the cartilages of a full-term infant who died 43 hours after birth. Extracts were made (a) from the costochondral junctions, including half-an-inch of bone and of cartilage on either side of the line of qssification, (b) from the costal cartilages at their sternal ends, and (c) from the patellae. In (b) and (c) no sign of commencing ossification could be 'made out.