R. L. Van Etten

Crystal Structure of a Human Low Molecular Weight Phosphotyrosyl Phosphatase IMPLICATIONS FOR SUBSTRATE SPECIFICITY

The low molecular weight phosphotyrosine phosphatases (PTPases) constitute a distinctive class of phosphotyrosine phosphatases that is widely distributed among vertebrate and invertebrate organisms. In vertebrates, two isoenzymes of these low molecular weight PTPases are commonly expressed. The two human isoenzymes, HCPTPA and HCPTPB, differ in an alternatively spliced sequence (residues 40–73) referred to as the variable loop, resulting in isoenzymes that have different substrate specificities and inhibitor/activator responses. We present here the x-ray crystallographic structure of a human low molecular weight PTPase solved by molecular replacement to 2.2 Å. The structure of human low molecular weight PTPase is compared with a structure representing the other isoenzyme in this PTPase class, in each case with a sulfonate inhibitor bound to the active site. Possible aromatic residue interactions with the phosphotyrosine substrate are proposed from an examination of the binding site of the inhibitors. Differences are observed in the variable loop region, which forms one wall and the floor of a long crevice leading from the active-site loop. A set of residues lying along this crevice (amino acids 49, 50, and 53) is suggested to be responsible for differences in substrate specificity in these two enzymes.

Immunohistochemistry of acid phosphatase in the human prostate: normal and pathologic. Cytochemistry and biochemistry of acid phosphatases II.

SummaryThree different antisera against human prostatic acid phosphatase were used for direct and indirect immunohistochemical demonstration of acid phosphatase in paraffin sections of infantile and adult normal, hyperplastic and carcinomatous prostatic tissue. All antisera were prepared in rabbits. Antiserum A was prepared from highly purified acid phosphatase extracted from autopsy specimens. Antiserum B was a concentrate of a commercial antiserum used in radioimmunoassay and was prepared from purified extracts of human seminal fluid. Antiserum C was a peroxidaseconjugated antiserum prepared from purified extracts of human seminal fluid.The specificity of the three antisera was compared using different immunohistochemical methods and tissues. It was comparably high in all three antisera which gave only slightly different staining results in prostatic tissue. The staining results in prostatic carcinoma were only dependent on the titer of the respective antiserum. Carcinomas with a cribriform growth pattern showed variable staining, but always had a positive immunoreaction, provided the titer of the antiserum was sufficiently high.Striking differences were observed in metaplastic, atrophic and hyperplastic prostatic epithelium. The most intense reaction was observed in atrophic glands; it was much less intense in hyperplastic and normal epithelium and negative or slightly positive in metaplastic epithelium.

Properties and Chemical Applications of 18O Isotope Shifts in 13C and 15N Nuclear Magnetic Resonance Spectroscopy

Isotope effects may be broadly classified as intrinsic isotope effects (either primary isotope effects or secondary isotope effects), equilibrium isotope effects, or solvent isotope effects. In nuclear magnetic resonance (NMR) spectroscopy the most intensely studied and widely used of these isotope effects are the (intrinsic) secondary isotope effects, which arise because isotopic substitution in a molecule changes the shielding of other nuclei in the molecule. Thus, NMR signals of chemically identical nuclei in different isotopomers may have different chemical shifts. In general, the chemical shifts of nuclei in isotopomers with the heavier isotopes are upfield with respect to the lighter isotopes within a series, as for example the isotopes of hydrogen, the isotopes of oxygen, etc. The magnitudes of these secondary isotope effects are calculated as the differences in the chemical shifts for the different isotopomers, and are called isotope effects, isotope-induced shifts, or simply, isotope shifts.

Demonstration of prostatic-type acid phosphatase in non-lysosomal granules in the crypt epithelium of the human duodenum.

SummaryHuman prostatic-type of acid phosphatase has been demonstrated by biochemical methods to be expressed in a number of cells and tissues in addition to the prostate gland. However, the function of this activity is unknown, nor has the enzyme been convincingly localized at the cellular level in any non-prostatic tissues. Using biochemical and immunocytochemical methods, we demonstrate that human intestinal epithelium contains both a lysosomal and prostatic type of acid phosphatase. The prostatic-type enzyme is present only in the epithelium of the crypts and to a lesser extent in the transitional zone at the base of the villi, in contrast to the widely-distributed lysosomal type. The prostatic enzyme is contained in granules that do not react with anti-lysosomal acid phosphatase and are probably secretory in nature.