Acid phosphatase enzyme measurements are regularly performed in connection with the diagnosis and treatment of human prostatic cancer. In addition to carcinoma of the prostate, changes in acid phosphatase levels occur in other types of malignant growth, in hairy cell leukemia, in the congenital disorder known as Gaucher's disease, and in a fatal genetic disease characterized by a lack of acid phosphatase. Despite this, little is known about the structural and catalytic properties, or the biological role, of the diverse group of enzymes known as acid phosphatases. The present project continues an investigation of the fundamental enzymology and protein chemistry of acid phosphatases. The comparative biochemistry, substrate specificity, intracellular location, structure and mechanism of action of acid phosphatase enzymes from human prostate, human seminal fluid, bovine heart and human placenta are under study. The structural basis of isoenzyme variation is being determined for the case of human prostatic acid phosphatase. Protein sequence data has been obtained, the enzyme has been cloned and the establishment of the cDNA sequence is nearly complete. Active site peptides of the homologous human prostatic and human lysosomal acid phosphatases will be isolated using several distinct approaches involving radiolabeling with substrates as well as derivatization with unique active site- directed photolabile reactants. Because of their size, kinetic properties, regulatory properties and intracellular locations the low molecular weight human placental and bovine heart acid phosphatases differ from the much larger, dimeric lysosomal and prostatic (secretory) acid phosphatases. Consequently, these low molecular weight acid phosphatases will also be sequenced at the peptide level and they will be cloned and sequenced at the cDNA level. Regulatory interactions of the bovine heart and human placental acid phosphatases are being studied in order to test the hypothesis that these enzymes participate in a kinase/phosphatase regulatory cycle. The substrate specificities of acid phosphatases are being established by systematic variation of portions of naturally occurring substrates. The three-dimensional structures of low molecular weight acid phosphatases will be established by a combination of approaches including use of 500 and 600 MHz nuclear magnetic resonance spectroscopy.
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