Resumen

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 k_cat/K_m, k_cat and K_m, as well as on the absolute temperature profile of k_cat/K_m, 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 k_cat/K_m equals to k₁ and thus ES is formed and destroyed in the course of a series of consecutive reactions governed by the dynamic constant K_S = 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 pK_a-value 3.85, necessary for efficient catalysis.

Palabras llave : Porcine Pancreas Lipase; mechanism of hydrolysis; p-nitrophenyl laurate.