Superactivity and conformational changes on -Chymotripsin upon interfacial binding to cationic micelles.

CELEJ M.S.,; D´ANDREA, M-G.,; CAMPANA P.T.,; FIDELIO, G.D.,; BIANCONI, M.I

BIOCHEMICAL JOURNAL

Año: 2004 vol. 378 p. 1059 - 1059

0264-6021

p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt">The catalytic behaviour of alpha-CT (alpha-chymotrypsin) is affected by cationic micelles of CTABr (hexadecyltrimethylammonium bromide). The enzyme-micelle interaction leads to an increase in both the V(max) and the affinity for the substrate p -nitrophenyl acetate, indicating higher catalytic efficiency for bound alpha-CT. The bell-shaped profile of alpha-CT activity with increasing CTABr concentrations suggests that the micelle-bound enzyme reacts with the free substrate. Although more active with CTABr micelles, the enzyme stability is essentially the same as observed in buffer only. Enzyme activation is accompanied by changes in alpha-CT conformation. Changes in tertiary structure were observed by the increase in intensity and the red shift in the alpha-CT tryptophan fluorescence spectrum, suggesting the annulment of internal quenching and a more polar location of tryptophan residues. Near-UV CD also indicated the tra