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Biomedical subjects

I B Wilson

Publications and source records attributed to I B Wilson.

At least 109 records · Page 6Linked to original sources
PubMed1978

A new chromogenic substrate for angiotensin-converting enzyme.

The compound para-nitrobenzyloxycarbonylglycyl-(S-4-nitrobenzo-2-oxa- 1,3-diazole)-L-cysteinylglycine [NO2ZGly(S-NBD)CysGly] with an absorption maximum at 423 nm is readily hydrolyzed by angiotensin-converting enzyme (EC 3.4.15.1. peptidlyldipeptide hydrolase) to yield the S-benzfurazan derivative of cysteinylglycine. An internal S-->N shift occurs immediately to yield the N-benzfurazan derivative which in turn reacts with the sulfhydryl reagent 4,4'-dithiodipyridine to produce the mixed disulfide with an intense absorption at 461 nm. The maximum difference in molar absorptivity of 13,000 M-1 cm-1 occurs at 470 nm.

Chromogenic Compounds↗
PubMed1978

Muscarinic cholinergic receptors in murine lymphocytes: demonstration by direct binding.

Using [3H]quinuclidinyl benzilate as a specific cholinergic muscarinic ligand, it has been demonstrated that lymphocytes have muscarinic binding sites. There are approximately 200 sites per cell and the dissociation constant for quinuclidinyl benzilate is approximately 1 X 10(-9) M. Quinuclidinyl benzilate receptor binding is blocked by atropine and oxotremorine.

Animals↗
PubMed1978

A fluorogenic substrate for angiotensin-converting enzyme in plasma.

A simple, sensitive, and reproducible assay for angiotensin-converting enzyme is described. It is based on the hydrolysis of the minimally fluorescent substrate p-nitrobenzyloxycarbonylglycyl-L-tryptophylglycine to the products p-nitrobenzyloxycarbonylglycine and the highly fluorescent L-tryptophylglycine. The L-tryptophylglycine was analyzed by fluorometry (lambda excitation = 285 nm; lambda emission = 350 nm). The mean value for human plasma (serum) is 16.5 nmol of substrate hydrolyzed per minute per milliter of plasma under the described assay conditions.

Dipeptides↗
PubMed1978

Serum alkaline phosphatase isoenzymes in lymphoproliferative diseases.

A new isoenzyme of alkaline phosphatase (EC 3.1.3.1) has been reported to occur in sera from patients with lymphoproliferative diseases. This enzyme is characterized by an inability to hydrolyze cysteamine S-phosphate. We find that the 5,5'-dithobis(2-nitrobenzoic acid)-coupled assay method for cysteamine S-phosphate hydrolysis is not suitable for serum, and we were unable to confirm the existence of this isoenzyme in serum by this assay method. We were unable to detect to detect this new isoenzyme by polyacrylamide gel electrophoresis with activity stains or by the reported high sensitivity of this enzyme to inhibition by cysteamine S-phosphate when p-nitrophenyl phosphate is the substrate. We were also unable to confirm reports of a unique inhibitor of normal alkaline phosphatase in the serum of patients with infectious mononucleosis.

Alkaline Phosphatase↗
PubMed1977

Effects of quaternary ligands on the inhibition of acetylcholinesterase by arsenite.

Arsenite inhibits acetylcholinesterase in a second-order reaction. The rate and equilibrium constants depend upon pH and have values on the order of 10(2) M-1 min-1 and 10(5) M (dissociation), respectively. Some quaternary ammonium ligands completely block the arsenite inhibition of the enzyme, others decrease the rate of the reaction and some, notably pyridine-2 aldoxime methiodide, greatly accelerate the rate of the reaction, up to 220-fold. Accelerators may bind at a separate enzyme site distinct form the anionic site involved in substrate binding. Although the kinetic data are consistent with a covalent reaction between arsenite and acetylcholinesterase, chemical evidence excludes the involvement of sulfhydryl groups which are usually implicated in arsenite inhibition.

Ammonia↗
PubMed1975

Reactivation and aging of diphenyl phosphoryl acetylcholinesterase.

Acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) is readily in hibited by 10(-5) M diphenylphosphorochloridate even though the inhibitor hydrolyzes in a few seconds. The fluoridate is a much weaker inhibitor. The inhibited enzyme, diphenyl phosphoryl enzyme spontaneously recovers only about 50% of its activity with a half time of about 17 min at pH 7.0 and 6 min at pH 8.0. The fact that only 50% of the original activity returns is due to aging. The rates of reactivation and aging can be very greatly increased by a few percent of an organic solvent. Depending on the solvent even 1% may increase the rates by a factor of 5 or 6. The highest increase in rate was 70-fold. Quaternary NH+4 also increases the rates. Organic solvents and NH+4 also accelerate the reactivation of the much more stable diethyl phosphoryl enzyme derivative.

Acetylcholinesterase↗