Brazilian Archives of Biology and Technology
versión impresa ISSN 1516-8913
KOKKINOU, Marina; THEODOROU, Leonidas G. y PAPAMICHAEL, Emmanuel M.. Aspects on the catalysis of lipase from porcine pancreas (type VI-s) in aqueous media: development of ion-pairs. Braz. arch. biol. technol. [online]. 2012, vol.55, n.2, pp. 231-236. ISSN 1516-8913. http://dx.doi.org/10.1590/S1516-89132012000200007.
This article reports a first contribution for the elucidation of catalytic mechanism of Lipase from porcine pancreas, type VI-s (PPL), in hydrolyzing an ester substrate in aqueous media. The conclusions were based on the pH-profiles of Michaelis-Menten parameters kcat/Km, kcat and Km, as well as on the absolute temperature profile of kcat/Km, obtained during the hydrolysis of p-nitrophenyl laurate by PPL. It was found that (a) PPL performs catalysis by means of ion pairs formed either as Ser152-Ο-/His263-Im +H and/or Carbonyl-Ο-/His263-Im +H, (b) the parameter kcat/Km equals to k1 and thus ES is formed and destroyed in the course of a series of consecutive reactions governed by the dynamic constant KS = k2/k1, and (c) the hydrolysis of substrate is assisted by a hydrogen bond developed between deprotonated Asp176 and the positively charged imidazole of His263 across a pKa-value 3.85, necessary for efficient catalysis.
Palabras llave : Porcine Pancreas Lipase; mechanism of hydrolysis; p-nitrophenyl laurate.