Jun 1, 1976

Estimation of tryptophyl and tyrosyl exposure in tryptophan-rich proteins by ultraviolet difference spectrophotometry. Lysozyme and Chymotrypsinogen

Journal of Biochemistry
T Izumi, H Inoue

Abstract

Ultraviolet difference absorption spectra produced by ethylene glycol were measured for hen lysozyme [EC 3.2.1.17] and bovine chymotrypsinogen. N-Acetyl-L-tryptophanamide and N-acetyl-L-tyrosinamide were employed as model compounds for tryptophyl and tyrosyl residues, respectively, and their ultraviolet difference spectra were also measured as a function of ethylene glycol concentration. By comparison of the slopes of plots of molar difference extinction coefficients (delta epsilon) versus ethylene glycol concentration for the proteins with those of the model compounds at peak positions (291-293 and 284-287 nm) in the difference spectra, the average number of tyrosyl as well as tryptophyl residues in exposed states could be estimated. The results gave 2.7 tryptophyl and 1.9 tyrosyl residues exposed for lysozyme at pH 2.1 and 2.6 tryptophyl and 3.4 tyrosyl residues exposed for chymotrypsinogen at pH 5.4. The somewhat higher tyrosyl exposure of chymotrypsinogen, compared with the findings from spectrophotometric titration and chemical modification, was not unexpected, because delta epsilon285 was larger than delta epsilon292, and the situation is discussed with reference to preferential interaction of ethylene glycol with the tyr...Continue Reading

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Mentioned in this Paper

Tryptophyl-arginyl-tryptophyl-tryptophyl-tryptophyl-tryptophanamide
Chromophore
Tryptophan
Chymotrypsinogen A
Ethylene Glycol Measurement
Lysozyme Test
Bos taurus
Cyclo(tyrosyl-tyrosyl)
Cattle Diseases
Plasma Protein Binding Capacity

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