Thermal behavior of bovine β-trypsin at physiological temperature range

• Published in: Archives of biochemistry and biophysics Vol. 204; no. 1; pp. 109 - 116
• Main Authors: De Souza Otero, Angela, Rogana, Edyr, Mares-Guia, Marcos
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.1980
• Subjects: Animals; Cattle; Enzyme Activation; Guanidines - pharmacology; Kinetics; Mathematics; Temperature; Thermodynamics; Trypsin - metabolism
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/0003-9861(80)90012-0

The effects of temperature on the steady-state kinetics of β-trypsin hydrolysis of α- Ntosyl- l-arginine methyl ester ( k cat, K m ) and its inhibition by phenylguanidinium ion ( K i ) were studied in the temperature range 27–37 °C, at 1 °C intervals, pH 8.0. Within this temperature range inhibition of β-trypsin by phenylguanidine was strictly competitive. The Eyring and van't Hoff plots were nonlinear; interpretation of the data was based on two possible alternatives: in the first, there occurs a thermal transition centered at 31 °C, characterized by ΔH° = 42.2 ± 8.7 kcal/ mol and ΔS ° = 138 ± 29 e. u. According to the second interpretation the phenomenon would be determined by a large value of Δ Cp; its value was estimated to be Δ Cp = −7192 cal/ deg · mol. A decision as to what interpretation is more adequate must wait until further experimental information is obtained.