Human Placental Acid Phosphatase

More recently, DiPietro and Zengerle (D13) studied the properties of acid phosphatase obtained from homogenates of perfused placentas centrifuged at 600p for 5 minutes to eliminate cellular debris. The resultant supernatant was then centrifuged at 96,600fif for 45 minutes in 

The pattern of hydrolysis of various substrates by these three isoenzymes also showed marked differences. When the velocity of hydrolysis of p-nitrophenyl phosphate was arbitrarily set at 100, the rates for isoenzyme I were a-naphthyl phosphate, 59 pyridoxine 5-phosphate, 40. 

The corresponding rates for isoenzyme II were 50 and 66, and those for isoenzyme III were 7 and 2. The velocity of hydrolysis of other phosphate esters, such as glucose 6-phosphate or glucose 1-phosphate were, in general, low or negligible. An interesting property of isoenzyme III, not shared by either I or II, was the stimulation of its action on p-nitro-phenyl phosphate by various purines. For example, 5 mM adenine increased the activity by 83%, and 0.1 mM A -benzyladenine or iV -methyladenine by 35% and 34%, respectively. 6-Ethylmercaptopurine at a concentration of 1 mM had a stimulatory effect of 168%. 

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Amino Acid Composition of Human Placental Alkaline Phosphatase... 

Fig. 29. Optimum pH of hydrolysis of human placental alkaline phosphatase by neuraminidase. The liberated sialic acid was measured by the Warren-thiobarbiturate procedure, using iV-acetylneuraminic acid as the standard (G6a).

Henthorn PS, Raducha M, Edwards YH et al (1987) Nucleotide and amino acid sequences of human intestinal alkaline phosphatase close homology to placental alkdine phosphatase. Proc Natl Acad Sci U S A 84 1234-1238... 

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