Biomedical subjects
G L Tritsch
Publications and source records attributed to G L Tritsch.
A model for hydropathy-based peptide interactions.
Two peptides are specified when the noncoding DNA strand is read in the 5' to 3', or the 3' to 5' direction, and both peptides form strong complexes with the natural peptide, as found by J. E. Blalock and K. L. Bost with ACTH [1986) Biochem. J. 234, 679-683). We report here that strong hydropathic complementarity (pairing of hydrophobic with hydrophilic residues), the assumed basis of these interactions, is obtained only if the peptide resulting from reading in the 3' to 5' direction is aligned parallel to the natural peptide, or if the peptide derived by opposite reading of the DNA is aligned antiparallel to it. Complementary is abolished in other alignments, including all staggered ones. In the appropriate alignments of the constructs the amino acid residues opposite one another are specified by a pair of complementary codons in the DNA; Blalock and Bost have indeed shown that complementary pairs of codons specify amino acids of opposite hydropathy. A model is proposed to explain how hydropathic complementarity can lead to interaction between peptides. We propose that in the interacting peptides hydrophilic residues of both chains are oriented toward the aqueous solvent, while the hydrophobic ones form the interphase between the two chains. Tight packing is made possible by the stipulation that whenever a hydrophilic residue turns toward the aqueous phase, a space is liberated which can accommodate a hydrophobic residue from the opposing chain. This entropy-driven configuration can lead to strong interactions between portions of peptides consisting of hydropathically complementary residues.
Ecto-enzyme activity of human erythrocyte adenosine deaminase.
Adenosine deaminase is found primarily in the cytoplasm of many cell types. In the human erythrocyte, about 30 per cent of the total adenosine deaminase activity is membrane associated, and about two-thirds of this is inactivated by treatment of intact erythrocytes with the nonpenetrating reagent diazotized sulfanilic acid, without affecting lactate dehydrogenase, a soluble cytoplasmic enzyme. This indicates that within the cell membranes, the catalytic site of about two-thirds of the adenosine deaminase faces the external medium, i.e., ecto adenosine deaminase. Localization of adenosine deaminase activity at the cell membrane is demonstrated directly by electron microscopy by use of the substrate 6-Chloropurine ribonucleoside, which is dechlorinated by adenosine deaminase to produce Cl-, which is precipitated at its locus of formation by added Ag+, and the precipitated AgCl converted into the electron dense Ag0 upon exposure to light. From the Hydropathic Profile of the amino acid sequence of adenosine deaminase it is evident that there are two hydrophobic domains of sufficient length to span a biological membrane, and it is proposed that these domains could function to anchor the enzyme to the membrane. The importance of adenosine deaminase is indicated by the fatal immuno-deficiency which results from untreated genetic adenosine deaminase deficiency. It may be important to determine whether the amount of ecto adenosine deaminase activity is better suited to assess the clinical status of adenosine deaminase deficient patients that the currently used total cellular enzyme activity.
Similarity in the hydropathy profile of tyrosyl-t RNA synthetase and the estrogen receptor.
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Adenosine deaminase activity associated with phagocytic vacuoles. Cytochemical demonstration by electron microscopy.
Adenosine deaminase activity has been localized within the cell membrane and it surrounds phagocytic vacuoles in mouse macrophages. Adenosine deaminase is thus strategically located to direct metabolic flux through the enzymes of the purine catabolic pathway. Xanthine oxidase, a key enzyme of this pathway, produces superoxide during its reaction with its substrates. Enzyme activity was visualized for electron microscopy by means of hydrolysis of 6-Chloropurine ribonucleoside to produce Cl-, which is precipitated with Ag+. The latter is converted into Ag0 by light, and the resulting deposit is visualized with the electron microscope.
Kinetics of formation of renotropic growth factor.
In the Wistar/Furth rat, twenty-four hours after unilateral nephrectomy, the remaining contralateral kidney produces maximum amounts of renotropic growth factors. These factors stimulate tumor growth in recipient rats with s.c. Wilms tumor, but have no effect on kidney weight. In tumor-free recipients, kidney hypotrophy results when the factors are administered.
Specificity of renotropin receptors in murine Wilms tumor model.
Contralateral kidneys, removed forty-eight hours after unilateral nephrectomy, contain renotropic growth factors with different effects on normal kidney and Wistar/Furth rat Wilms tumor. Receptors on tumor cells bind factors which, when eluted followed by in vivo bioassay, stimulate the growth of Wilms tumor. Receptors on normal kidney cortex cells bind factors which, when eluted, produce kidney hypotrophy in nontumor-bearing rats.
Purine catabolism as a source of superoxide in macrophages.
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Modulation of macrophage superoxide release by purine metabolism.
Metabolic flux through the purine salvage pathway appears to modulate superoxide secretion by elicited macrophages. Exogenous adenosine, the first substrate of this pathway, stimulates superoxide secretion, and Allopurinol, a specific inhibitor of xanthine oxidase, inhibits superoxide secretion. The effects of these agents are additive since it was possible for each to neutralize the effects of the other when given in combination. In these experiments, the purine salvage pathway was responsible for over ten times the superoxide production attributable to the NADPH oxidase system.
Validity of the continuous spectrophotometric assay of Kalckar for adenosine deaminase activity.
Both adenosine and inosine obey Beer's law to 1.0 mM at 265 nm and pH 7.4 at 25 degrees C. Murphy et al. (1) claimed serious deviation from Beer's law above 200 microM for both substances, and concluded that the assay of adenosine deaminase activity based on recording spectrophotometric change at 265 nm as originally suggested by Kalckar produces anomalous results. The data herein presented show that this is not so, and that the large number of published studies of adenosine deaminase activity assayed by this method are indeed valid and should not be dismissed as artifactual as suggested by Murphy et al.
Purine salvage pathway enzyme activity in tuftsin-stimulated macrophages.
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Positive correlation between superoxide release and intracellular adenosine deaminase activity during macrophage membrane perturbation regardless of nature or magnitude of stimulus.
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Removal of superoxide dismutase activity from cytochrome C.
Commercially available cytochrome c contains sufficient superoxide dismutase activity to reduce its sensitivity in superoxide anion detection. A single passage through a column of Sephadex G-50 removes the superoxide dismutase, and appreciably increased the ability to cytochrome c to detect superoxide.
Adenosine deaminase activity and superoxide formation during phagocytosis at different cell densities.
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Adenosine deaminase activity and superoxide formation during phagocytosis and membrane perturbation of macrophages.
During phagocytosis and membrane perturbation, mouse macrophages generate superoxide in direct proportion to their intracellular adenosine deaminase activity. It is proposed that since adenosine deaminase controls the amount of substrate available to xanthine oxidase, and the latter produces superoxide during turnover of its substrates, the purine salvage pathway is an important contributor to the superoxide requirement of macrophages. It is further proposed that this may be the basis for the mechanism of the association of adenosine deaminase deficiency with immunodeficiency.
Adenosine deaminase specific activity in normal, benign hypertrophied and neoplastic human prostate tissue.
The finding that deficiency in the purine salvage pathway enzyme, adenosine deaminase (ADA), is associated with immunodeficiency suggests that this enzyme may be crucial for normal function of immunocompetent cells in man. We have therefore examined ADA activity in human prostatic tissue. Mean values were as follows: normal tissue, 0.37 mumol substrate turned over/h/mg protein; carcinoma, 0.33; benign prostatic hypertrophy (BPH), 1.22. ADA activity in normal and carcinoma prostate tissue differed significantly from BPH (p = 0.001), but were individually indistinguishable. Thus, there may be a cellular level of immunostimulation in BPH relative to normal prostatic tissue which is no longer detectable in overt carcinoma.
Positive correlation between adenosine deaminase activity and superoxide formation during phagocytosis.
Phagocytosis and membrane perturbation in mouse macrophages results in an increased superoxide ion production which is in direct proportion to the concomitant increase in adenosine deaminase activity. Since adenosine deaminase activity controls the amount of substrate available to xanthine oxidase, and the latter produces superoxide during turnover of its substrates, it is proposed that the purine salvage pathway is an important source of the superoxide requirement of macrophages. It is further proposed that this may be the basis, at least in part, for the mechanism of the association of immunodeficiency with adenosine deaminase deficiency.
Adenosine deaminase and nucleoside phosphorylase activities in normal human blood mononuclear cell subpopulations.
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