New role for leucyl aminopeptidase in glutathione turnover.
A manganese-dependent cysteinyl-glycine hydrolysing activity has been purified to electrophoretic homogeneity from bovine lens. The characterization of the purified enzyme (molecular mass of the native protein, molecular mass of the subunit and extensive primary structure analysis) allowed the unequivocal attribution of the cysteinyl-glycine hydrolysing activity, which is usually associated with alanyl aminopeptidase (EC 3.4.11.2) or membrane-bound dipeptidase (EC 3.4.13.19), to LAP (leucyl aminopeptidase; EC 3.4.11.1). Analysis of the pH dependence of Cys-Gly hydrolysis catalysed by LAP, supported by a molecular modelling approach to the enzyme-substrate conformation, gave insights into the ability of the enzyme to recognize Cys-Gly as a substrate. Due to the effectiveness of LAP in hydrolysing Cys-Gly (K(m)=0.57 mM, kcat=6.0x10(3) min(-1) at pH 7.4 and 25 degrees C) with respect to other dipeptide substrates, a new role for this enzyme in glutathione turnover is proposed.
Dipartimento di Fisiologia e Biochimica, Università di Pisa, via S. Maria 55, 56126 Pisa, Italy.
Mario
M
Cappiello
Alessandra
A
Lazzarotti
Francesca
F
Buono
Andrea
A
Scaloni
Chiara
C
D'Ambrosio
Pietro
P
Amodeo
Blanca L
BL
Méndez
Paolo
P
Pelosi
Antonella
A
Del Corso
Umberto
U
Mura
D000818:Animals; D002417:Cattle; D004150:Dipeptidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004151:Dipeptides / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007908:Lens, Crystalline / Q000201:enzymology; D007931:Leucyl Aminopeptidase / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D008958:Models, Molecular
D004151:Dipeptides; D007931:Leucyl Aminopeptidase; C019974:cysteinyl-glycine dipeptidase; D004150:Dipeptidases; D005978:Glutathione