The existing purification procedure for purple acid phosphatase from bovine spleen was relatively inefficient and has been extended using cellulose phosphate chromatography. The recovery is much higher than that obtained with other tecbniques. The purity is increased by two and a half fold.
The Michaelis-Menten constant, Km, for p-nitrophenyl phosphate has been found to be 2.0 mM. A plot of 1/Vo versus 1/(S) according to the Lineweaver-Burk equation was used to calculate the Km.
The relationship between the structural features of inhibitors and the binding specificity of the enzyme is investigated through the inhibition studies of the structural aoalogues of the substrate, PNPP. The results suggest that the binding specificity is not related to the charge distribution on the aromatic moieties of the structual analogues, but related to the nature of phosphorus linkage.
A catalytic reaction pathway is postulated from the products inhibition studies. 吾人在此實驗中把經由文獻純化法所得的酵素再進一步用磷酸纖維樹脂的色層分析法處理過,結果純度增加了兩倍半。吾人測得此酵素對於一硝基苯磷酸脂的麥˙米氏常數測得為2.0mM,實驗結果亦顯示此酵素的催化作用的高度選擇性和基質的結構上的苯環部分所帶的電荷無關但和磷脂部分的不可或缺有較大的關係(根據產物抑制作用的試驗結果),吾人亦推測一種可能的催化作用機轉,亦即水解過程伴隨著對一硝基酚。(產物之一)的先擴散而無機磷酸隨後擴散。
把此酵素預先用含Fe(Ⅱ)不含PNPP及維生素丙的緩衝溶液處理過後,發現Fe(Ⅱ)大大的加強了酵素的活性。反之把酵素預先用含維生素丙,不含Fe(Ⅱ)及PNPP的緩衝溶液處理過後,發現維生素丙大大的抑制了酵素的活性。在無PNPP,Fe(Ⅱ)及維生素丙存在下,Fe(Ⅲ)本身對酵素沒有活化作用。