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Lipase stereoselectivity and regioselectivity toward three isomers of dicaprin: A kinetic study by the monomolecular film technique
Author(s) -
Rogalska Ewa,
Nury Sylvie,
Douchet Isabelle,
Verger Robert
Publication year - 1995
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.530070703
Subject(s) - chemistry , lipase , regioselectivity , enantiomer , glyceride , stereoselectivity , stereochemistry , substrate (aquarium) , diglyceride , chirality (physics) , candida antarctica , enzyme , organic chemistry , catalysis , fatty acid , oceanography , physics , geology , nambu–jona lasinio model , chiral symmetry breaking , quantum mechanics , quark
Here we present a kinetic study on the steroselectivity and regioselectivity of 23 purified lipases of animal and microbial origin. This work, concerning a general problem of the mechanism of lipase–substrate molecular recognition, was performed using pure dicaprin isomers: 1,2‐ sn ‐dicaprin, 2,3‐sn‐dicaprin, and 1,3‐ sn ‐dicaprin spread as monomolecular films at the air–water interface. The first two isomers are optically active antipodes (enantiomers), forming stable films up to 40 mN m −1 , while the last is a prochiral compound, with a surface pressure of collapse of 32 mN m −1 . To our knowledge, this is the first report on the use of three diglyceride isomers as lipase substrates under identical and controlled physicochemical conditions. The lipases tested display a typical behaviour, characteristic of each enzyme, which allowed us to classify the lipases in groups according to (1) the profiles of enzyme velocity as a function of surface pressure, (2) their preferences for a given diglyceride isomer, quantified using new parameters termed steroselectivity index (S.I.), vicinity index (V.I.), and surface pressure threshold (S.P.T.). The general observation, true for all the enzymes tested, is that the three substrates are well differentiated, and the differentiation is more pronounced at high interfacial energy (low surface pressure). This observation supports our hypothesis that lipase conformational changes, resulting from the enzymesurface interaction, affect the enzymes' specificities. Generally speaking, the stereopreference for either sn ‐1 or sn ‐3 position on glycerides is maintained both in the case of di‐ and tri‐glycerides. © 1995 Wiley‐Liss, Inc.