Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alpha-crystallin exhibits variable inhibition of several members of the chymotrypsin family of proteinases. Complete inhibition of elastase was obtained by the addition of either alpha-crystallin or a sonicated preparation of the water-insoluble fraction from bovine lens. Little or no inhibition was seen, however, with either beta-crystallin or bovine serum albumin under the same conditions. Complete binding of elastase was demonstrated by Sephadex G-100 gel filtration chromatography, and a direct correlation between binding and inhibition was obtained. This observation permitted us to do a Scatchard analysis of the inhibition data. Scatchard plots for the binding of elastase gave a biphasic response suggesting two separate binding sites. These sites had Kd values of 15 and 40 nM for alpha-crystallin and 6 and 42 nM for the bovine water-insoluble fraction. Similarly, a Dixon plot exhibited a Ki value of 3 nM and was consistent with non-competitive inhibition. One mole of alpha-crystallin (8 x 10(5) Da), or an equivalent amount of water-insoluble protein, bound from 13 to 19 mol of elastase which were about equally divided between the higher and lower affinity sites. Saturation studies confirmed 20 and 16 elastase binding sites per 8 x 10(5) Da for alpha-crystallin and water-insoluble protein, respectively. DFP-elastase was capable of binding to alpha-crystallin suggesting that a proteolytic cleavage was not required for complex formation. Stability measurements showed a linear return to 60% of the original activity over a 30-min period. Therefore, the interaction between elastase and alpha-crystallin resembles that of a heterologous protease:inhibitor complex in both binding and stability.
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PMID:Characterization of the elastase inhibitor properties of alpha-crystallin and the water-insoluble fraction from bovine lens. 154 28

Bovine lens alpha-crystallin inhibited both porcine pancreatic elastase (PPE) and human neutrophil elastase (HNE), but not in the same manner. PPE was immediately inhibited with a stoichiometry of 10 moles of PPE inhibited per mole of alpha-crystallin. The inhibition was markedly decreased by the addition of even low levels of salts. The inhibition was transient, as PPE activity returned to normal with a t1/2 of 30 min even in low salt. HNE required a short preincubation to show maximum inhibition with a stoichiometry of approximately one mole of HNE inhibited per mole of alpha-crystallin. The inhibition of HNE was only slightly decreased by the addition of 0.1 M salt, and HNE activity returned slowly exhibiting a t1/2 of 30 hrs under these conditions. The inhibition of each enzyme by alpha-crystallin was evaluated by Dixon plots giving Ki values of 1.5 nM for PPE and 0.25 nM for HNE. DFP-trypsin was able to compete with PPE for binding to alpha-crystallin and cause the release of PPE already bound to alpha-crystallin. The inhibition of HNE, however, was unaffected by the addition of DFP-trypsin. A mixture of HNE and alpha-crystallin in 0.1 M NaCl was incubated at 25 degrees C for 6 hours. Aliquots showed a slow, continuous cleavage of the alpha-crystallin subunits by SDS-PAGE, but little or no increase in HNE activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A comparison of the inhibition of porcine pancreatic elastase and human neutrophil elastase by alpha-crystallin. 795 8

We have evaluated the potential of plasma albumin to provide a sensitive biomarker of exposure to commonly used organophosphorus pesticides in order to complement the widely used measure of acetylcholinesterase (AChE) inhibition. Rat or human plasma albumin binding by tritiated-diisopropylfluorophosphate ((3)H-DFP) was quantified by retention of albumin on glass microfibre filters. Preincubation with unlabelled pesticide in vitro or dosing of F344 rats with pesticide in vivo resulted in a reduction in subsequent albumin radiolabelling with (3)H-DFP, the decrease in which was used to quantify pesticide binding. At pesticide exposures producing approximately 30% inhibition of AChE, rat plasma albumin binding in vitro by azamethiphos (oxon), chlorfenvinphos (oxon), chlorpyrifos-oxon, diazinon-oxon and malaoxon was reduced from controls by 9+/-1%, 67+/-2%, 56+/-2%, 54+/-2% and 8+/-1%, respectively. After 1 h of incubation with 19 microM (3)H-DFP alone, the level of binding to rat or human plasma albumins reached 0.011 or 0.039 moles of DFP per mole of albumin, respectively. This level of binding could be further increased by raising the concentration of (3)H-DFP, increasing the (3)H-DFP incubation time, or by substitution of commercial albumins for native albumin. Pesticide binding to albumin was presumed covalent since it survived 24 h dialysis. After dosing rats with pirimiphos-methyl (dimethoxy) or chlorfenvinphos (oxon) (diethoxy) pesticides, the resultant albumin binding were still significant 7 days after dosing. As in vitro, dosing of rats with malathion did not result in significant albumin binding in vivo. Our results suggest albumin may be a useful additional biomonitor for moderately low-level exposures to several widely used pesticides, and that this binding differs markedly between pesticides.
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PMID:Albumin binding as a potential biomarker of exposure to moderately low levels of organophosphorus pesticides. 1848 51