Kinetics of proton transfer reactions of lysozyme with p-nitrophenol near neutral pH—a study of dynamic properties of Glu 35 and His 15
✍ Scribed by Shin-Ichi Segawa; Yuzuru Husimi; Akiyoshi Wada
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1975
- Tongue
- English
- Weight
- 1001 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
Kinetics of proton transfer between lysozyme and a pH indicator p‐nitrophenol (p‐Np) were measured by the temperature‐jump method in a pH range of 6.0–7.0. Two well‐defined relaxation processes were observed. The fast process (τ ≃ 15 μsec) was also observed for a lysozyme derivative succinylated at the terminal α‐amino group of Lys 1. Therefore, the fast process was found to be attributable to the proton transfer reaction of His 15 with p‐Np. The slow process (τ ≃ 50 μsec) was found to be characteristic of the proton transfer reaction of Glu 35, because it disappeared completely in solution containing a lysozyme derivative having an ester crosslink between the carboxyl group of Glu 35 and indol C‐2 of Trp 108. The rate constants for proton transfer from Glu 35 and His 15 to p‐Np were found to be 9 × 10^6^/sec/M (±65%, 23°C) and 3 × 10^8^/sec/M (±20%, 25°C), respectively. These data indicate that the proton of the carboxyl group of Glu 35 is kinetically stabilized in lysozyme.