Steady-state and pre-steady-state kinetics for the hydrolysis of p-nitrophenyl esters of N-alpha-carbobenzoxy(-l-)amino acids catalyzed by leucine-proteinase were determined between pH 5 and 10 (I = 0.1 molar) at 23 +/- 0.5 degrees C. For the substrates considered: (a) the acylation step is rate-limiting in catalysis; (b) the pH profiles of k(cat) and k(cat)/K(m) reflect the ionization of two groups with pK(a) values ranging between 6.5 and 6.9, and 8.1 and 8.3 (probably, the histidine residue involved in the catalytic triad and the N-terminus, respectively); and (c) values of K(m) are pH independent. Among the substrates examined, N-alpha-carbobenzoxy-l-leucine-p-nitrophenyl ester shows the most favorable catalytic parameters and allows to determine an enzyme concentration as low as 5 x 10(-10) molar at the optimum pH value (approximately 7.5).

Aducci, P., Ascenzi, P., & Ballio, A. (1986). Esterolytic properties of leucine-proteinase, the leucine-specific serine proteinase from spinach (Spinacia oleracea L.). PLANT PHYSIOLOGY, 82(2), 591-593.

Esterolytic properties of leucine-proteinase, the leucine-specific serine proteinase from spinach (Spinacia oleracea L.)

ADUCCI, PATRIZIA;
1986

Abstract

Steady-state and pre-steady-state kinetics for the hydrolysis of p-nitrophenyl esters of N-alpha-carbobenzoxy(-l-)amino acids catalyzed by leucine-proteinase were determined between pH 5 and 10 (I = 0.1 molar) at 23 +/- 0.5 degrees C. For the substrates considered: (a) the acylation step is rate-limiting in catalysis; (b) the pH profiles of k(cat) and k(cat)/K(m) reflect the ionization of two groups with pK(a) values ranging between 6.5 and 6.9, and 8.1 and 8.3 (probably, the histidine residue involved in the catalytic triad and the N-terminus, respectively); and (c) values of K(m) are pH independent. Among the substrates examined, N-alpha-carbobenzoxy-l-leucine-p-nitrophenyl ester shows the most favorable catalytic parameters and allows to determine an enzyme concentration as low as 5 x 10(-10) molar at the optimum pH value (approximately 7.5).
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore BIO/04
Settore BIO/10
eng
leu proteinase, spinacia oleracea L, serine proteinase
Aducci, P., Ascenzi, P., & Ballio, A. (1986). Esterolytic properties of leucine-proteinase, the leucine-specific serine proteinase from spinach (Spinacia oleracea L.). PLANT PHYSIOLOGY, 82(2), 591-593.
Aducci, P; Ascenzi, P; Ballio, A
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2108/65029
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