Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the subcellular location of adenosine deaminase-complexing protein in the proximal renal tubules of rabbit kidney and its interaction with intravenously infused monomeric calf adenosine deaminase. Cortical tissue from non-infused animals, stained in suspension by the peroxidase-antiperoxidase method for complexing protein and embedded in resin, was examined by transmission electron microscopy. Positive staining indicated the presence of complexing protein on the surface of microvilli in the proximal tubules. Sections (1 micron) of resin-embedded cortex from infused rabbits, stained first for complexing protein and then for adenosine deaminase, were examined by light microscopy. After staining for complexing protein by indirect immunofluorescence, the sections were photographed and then immersed in buffer containing 6 M guanidine hydrochloride plus 2-mercaptoethanol for 3 hr at 60 degrees C to remove bound antibodies. The sections were then stained by the peroxidase-antiperoxidase method for infused enzyme. Vesicle-like apical structures, the basal membrane area and, as previously reported, the brush border of proximal tubule cells were positive for complexing protein. Vesicle-like structures and brush borders positive for complexing protein were also stained for adenosine deaminase. The basal membrane area did not stain. These results support the hypothesis that complexing protein can act as a receptor for adenosine deaminase.
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PMID:Evidence for receptor-mediated uptake of adenosine deaminase in rabbit kidney. 246 11

We have determined the stability curve of bovine adenosine deaminase via titrations with guanidine hydrochloride at pH = 6.3 from 5 to 65 degrees C. The data indicate that the enzyme undergoes an abrupt conformational transition at approximate, equals 29 degrees C, a finding supported by a temperature scan of the intrinsic enzyme fluorescence emission. Analysis of the data above and below this temperature with the modified Gibbs-Helmholtz equation allows for complete description of the equilibrium unfolding thermodynamics for either enzyme conformation. The high-temperature form of the enzyme is described by DeltaH degrees = 648 +/- 37 kJ/mole, DeltaC(P) = 23.2 +/- 2.5 kJ/mole-K, and a heat denaturational temperature T(h)(dn) = 72.5 +/- 0.9 degrees C. The low-temperature form is described by DeltaH degrees = 1284 +/- 47 kJ/mole, DeltaCP = 73.2 +/- 4.9 kJ/mole-K, and T(h)(dn) = 32.6 +/- 0.6 degrees C. Further thermodynamic analysis of the conformations that predominate at 38.3 degrees C, the bovine normal body temperature, and at 4 degrees C, where the crystals for x-ray structural analyses were formed, suggest that the stability of either form is due to favorable amino acid side chain nonpolar interactions with these interactions being much more optimized in the low-temperature conformation. We therefore conclude that the structure as determined by x-ray crystallographic methods cannot be the physiological structure. The data also suggest that the general calculation of enzyme stability curves from the extrapolation of heat denaturation data may inaccurately represent the enzyme stability as a low-temperature, nondenaturational transition is assumed not to exist. Further consequences in terms of general enzyme catalysis are also discussed.
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PMID:The stability curve of bovine adenosine deaminase is bimodal. 1243 75