Placenta acid phosphatase

Phosphates of pharmaceutical interest are often monoesters (Sect. 9.3), and the enzymes that are able to hydrolyze them include alkaline and acid phosphatases. Alkaline phosphatase (alkaline phosphomonoesterase, EC 3.1.3.1) is a nonspecific esterase of phosphoric monoesters with an optimal pH for catalysis of ca. 8 [140], In the presence of a phosphate acceptor such as 2-aminoethanol, the enzyme also catalyzes a transphosphorylation reaction involving transfer of the phosphoryl group to the alcohol. Alkaline phosphatase is bound extracellularly to membranes and is widely distributed, in particular in the pancreas, liver, bile, placenta, and osteoplasts. Its specific functions in mammals remain poorly understood, but it seems to play an important role in modulation by osteoplasts of bone mineralization. 

Beckman et al. (28) have studied the electrophoretic separation of the acid phosphatase activity in tissue extracts on starch gel at pH 8. They described four electrophoretic bands A, B, C, and D. Table IV (28) shows the distribution of activity in different organ extracts. The ABD pattern predominated in kidney BD in liver, intestine, heart, and skeletal muscle B in skin and D in pancreas. The C component was present in a large number of placentae but not in other adult organs. All four electrophoretic components were inhibited by d-(- -)-tartrate A contained sialic acid, D had a lower pH optimum and was more heat resistant than A, B, and C. Components C and D showed parallel electrophoretic behavior. In human skin fibroblasts grown in tissue culture, the acid phosphatase was generally high and the most common pattern was BD. Almost every culture showed some activity. The BD... 

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... 

BIO) carried out starch gel electrophoretic studies in 1200 individual placentas and in extracts of seven different organs obtained at autopsy from 14 individuals. The tissues showed different combinations of one or more bands of four distinct and, in some respects, biochemically different, acid phosphatase components. These were designated as A, B, C, and D in order of decreasing anodal mobilities. For example, in the case of heart tissue one individual showed three bands, ABD, whereas the remaining 13 showed a combination of two bands, BD. With regard to kidney tissue, 13 individuals had a combination of ABD, and one individual had a pair, BD. 

D13. DiPietro, D. L., and Zengerle, F. S., Separation and properties of three acid phosphatases from human placenta. J. Biol. Chem. 242, 3391-3396 (1967). 

N3-Phosphohistidine has been isolated from an alkaline hydrolysate of liver acid phosphatase (73) while N phosphohistidine has been isolated from prostate, placenta, and wheat germ acid phosphatases (74, 75). ]V3-Phosphohistidine is found in histone H4 (IV, F2al) (76). Phosphohistidines, substituted on either ring nitrogen atom, and c-N-phospholysine were isolated from a purified citrate cleavage enzyme (77). There is a good possibility that certain acidic nuclear proteins may contain e-iV-phospholysine and w-N-phosphoarginine (78). e-N-Phospholysine is present in histone I (FI) (78a). Phosphothreonine is found in certain proteins of which phosvitin is an example (79,80). 

In addition to its archetypical members, uteroferrin and bovine spleen add phosphatase, the class of purple add phosphatases includes proteins isolated from rat bone and. spleen spleens of patients with Gaucher s disease or leukemic reticuloen-dotheliosis equine uterine flushings bovine cortical bone giant ceU tumors human placenta and microorganisms . The plant enzymes include an Fe-Zn phosphatase from red kidney beans and an Fe-Fe or Mn(in) protein from sweet potato tubers . Although less well-defined and more heterogeneous than their mammalian counterparts, the color and iron content of the plant enzymes warrant their designation as purple acid phosphatases. 

Comparative distribution of acid phosphatase, nonspecific esterase and /3-glucuronidase in the placenta and fetal membranes (Christie, 1968) and some aspects of protea.se and /3-glucuronidase in the placental formation in rats have been reported by Autuori (1967). 

In mammals, APases are glycoproteins essential in bone metabolism and phosphate transport. They are present as isozymes in different tissues including bone, intestine, kidney, and placenta. In E. coli, APase is a periplasmic enzyme which is not essential for phosphate metabolism. Note that E. coli also possesses a periplasmic acid phosphatase, a monomeric 45-kDa enzyme with active-site histidines. In contrast to the APase which is encoded by the phoA gene, the acid phosphatase is encoded by the appA gene. 

Alkaline phosphatase is an enzyme represented by various isoforms in many tissues such as liver, bone, intestine, placenta, some tumors and in leukocytes. Addition of 1 mM levamisole to the chromogen/substrate will inhibit endogenous alkaline phosphatase activity, with the exception of the intestinal isoform. If necessary, this can be blocked with a weak acid wash, such as 0.03 0.5 N HC1 or 1 M citric acid. 

The last treatment is the most gentle and should be used for labile antigens 2 For alkaline phosphatase, incubate the section in 20% acetic acid for 5 min, and then wash it in tap water. This treatment may destroy the antigen. An alternative for tissues other than the intestine is to make the substrate solution (Section 3.2.2.) in 1 mM levamisole (increase to 2 mM for tissues rich in alkaline phosphatase, e.g, kidney or placenta) see Note 10)... 

Alkaline phosphatase is an enzyme of the cellular membranes. Its isoforms can be found in liver, digestive tract, placenta, and some tumor tissues. Bone isoform, BALP, is a membrane enzyme of the osteoblasts. Bone, liver, and intestinal isoforms are the posttranslational modifications of the same isoenzyme exprimed by the same gene, and the difference among them lies in various ways of reaction with a saccharide component, sialic acid (M9). 

Alkaline phosphatase catalyzes the biochemical splitting of phosphoric acid ester. AP (W.M. Roberts, 1933) is found in the liver, bone, kidney, intestine, lung and placenta. A Regan isoenzyme can be detected as an ectopic variation of placental AP in tumour patients (10-30% of cases). The AP of the liver is located in the cytoplasm and in the membranes, primarily at the biliary pole. Placental AP is also present in the liver. The AP of bile duct epithelia is not elevated in healthy individuals. The serum activity of AP is predominantly due to the isoenzymes of the liver and osteoblasts only 14% are of renal origin. Half-life is 3-7 days. 

Alkaline phosphatases (ALP) are a group of enzymes found primarily in the liver (isoenzyme ALP-1) and bone (isoenzyme ALP-2). There are also small amounts produced by cells lining the intestines (isoenzyme ALP-3), the placenta, and the kidney (in the proximal convoluted tubules). What is measured in the blood is the total amount of alkaline phosphatase released from these tissues into the blood. As the name implies, this enzyme works best at an alkaline pH (pH 10), and thus the enzyme itself is inactive in the blood. Alkaline phosphatase acts by splitting off phosphorus (an acidic mineral), creating an alkaline pH. The primary importance of measuring alkaline phosphatase is to check the possibility of bone or liver diseases. ... 

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