Spleen phosphatases

An early analysis of the spleen enzyme showed the presence of hexose and hexo-samine A more recent study has demonstrated an enzyme from human hairy leukemic cells which appears identical to the purple spleen phosphatase, and which binds to ConA-Sepharose and is eluted with methylmannoside Very likely, therefore, the spleen enzyme, Uke uteroferrin, is a high mannose glycoprotein, but the structure of its carbohydrate has yet to be determined. In each protein the oligosaccharide chain appears to be attached to an asparagine residue (at position 97 in uteroferrin), since this residue was observable only after treatment with N-glycanase which removes N-asparagine-linked oUgosaccharides. ... 

Although reduction and activation are synonymous for the vast majority of the purple acid phosphatases, several exceptions exist. The Fe-Zn forms of uteroferrin and bovine spleen phosphatase do not require prior reduction to exhibit enzymatic activity . The Fe-Cu and Fe-Hg derivatives of uteroferrin also do not require activation and in fact, the Fe-Cu preparation is inactivated by reducing agents The recently described high molecular weight pink form of uteroferrin has enzymic properties identical to those of purple uteroferrin treated with 2-mercaptoethanoP. Finally, the sweet potato acid phosphatase, which may exist as an 02 dimer with separate mononuclear iron centers, does not require the addition of reductant to promote its enzymatic activity. ... 

The role of the Zn atom in E. coU alkaline phosphatase, which catalyzes the phosphorylation of serine 99 in the amino add sequence to form the covalent enzyme-phosphate intermediate is well understood. Unfortunately, knowledge of the molecular mechanisms underlying the enzymic activity of the purple add phosphatases is far more rudimentary. Spectroscopic studies utilizing inhibitors and perturbants (Sect. III.B.10), such as phosphate and molybdate, indicate that substrate binds close to the binuclear iron cluster of uteroferrin and bovine spleen phosphatase Most likely, the substrate interacts with the redox active iron of the pair . ... 

The adult male prostate contains abundant acid phosphatase which it secretes into the semen. The production of this enzyme is governed by the circulating levels of androgenic hormones. Castration or estrogen administration markedly reduces the prostatic urinary acid phosphatase of males. Other organs such as the liver, kidney, spleen, red cells and platelets also contain significant amounts of acid phosphatase. 

Figure 1. Characteristic EPR signals of Fe(II)Fe(III) sites in semimethemerythrinj (a), semimethemerythrinQ (b), reduced uteroferrin (c), reduced uteroferrin-molybdate complex (d), reduced bovine spleen purple acid phosphatase (e), reduced component A of methane monooxygenase (f). (Reproduced with permission from ref. 26. Copyright 1987 Elsevier.)...

Milk acid phosphatase has been purified to homogeneity by various forms of chromaotgraphy, including affinity chromatography purification up to 40 000-fold has been claimed. The enzyme shows broad specificity on phosphate esters, including the phosphoseryl residues of casein. It has a molecular mass of about 42 kDa and an isoelectric point of 7.9. Many forms of inorganic phosphate are competitive inhibitors, while fluoride is a powerful non-competitive inhibitor. The enzyme is a glycoprotein and its amino acid composition is known. Milk acid phosphatase shows some similarity to the phosphoprotein phosphatase of spleen but differs from it in a number of characteristics. 

Acid phosphatases are produced by erythrocytes, the liver, kidney, spleen, and prostate gland. The enzyme of the prostate gland is clinically important, because its increased activity in the blood can be an indication of prostate cancer. The phosphatase from the prostate gland is strongly inhibited by tartrate ion, but acid phosphatases from other tissues are not. How can this information be used to develop a specific procedure for measuring the activity of the acid phosphatase of the prostate gland in human blood serum ... 

Hog spleen acid DNase, as obtained by the above procedure, is completely free of contaminating phosphatase, exonuclease, and adenosine deaminase activities. The enzyme has a weak intrinsic hydrolytic activity on bis(p-nitrophenyl) phosphate and the p-nitrophenyl derivatives of deoxyribonucleoside 3 -phosphates (see Section III,D,3). 

Chersi et al. 103) have carried out extensive purification of spleen acid phosphatase. Spleen was fractionated to yield crude spleen nuclease II 104). This preparation was found to contain large quantities of non-... 

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