Competitive inhibition by substrates of the esterification reaction between l-phenylalanine and d-glucose catalysed by the lipases of Rhizomucor miehei and Candida rugosa |
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Authors: | Kenchaiah Lohith Balaraman Manohar Soundar Divakar |
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Institution: | (1) Fermentation Technology and Bioengineering Department, Central Food Technological Research Institute, Mysore, 570020, India;(2) Food Engineering Department, Central Food Technological Research Institute, Mysore, 570020, India |
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Abstract: | A kinetic study on esterification between d-glucose and l-phenylalanine catalysed by lipases from Rhizomucor miehei (RML) and Candida rugosa (CRL) in organic media investigated in detail showed that both the lipases followed a Ping-Pong Bi-Bi mechanism with two
distinct types of competitive inhibitions. Graphical double reciprocal plots and computer simulation studies showed that competitive
double substrate inhibition took place at higher concentrations leading to dead-end inhibition in the case of RML and in the
case of CRL, inhibition only by d-glucose at higher concentrations leading to dead-end lipase–d-glucose complexes. An attempt to obtain the best fit of these kinetic models through curve-fitting yielded in good approximation,
the apparent values of important kinetic parameters, RML: k
cat = 2.24 ± 0.23 mM h−1 (mg protein)−1, K
m l-phenylalanine = 95.6 ± 9.7 mM, K
m d-glucose = 80.0 ± 8.5 mM, K
i l-phenylalanine = 90.0 ± 9.2 mM, K
i d-glucose = 13.6 ± 1.42 mM; CRL: k
cat = 0.51 ± 0.06 mM h−1 (mg protein)−1, K
m l-phenylalanine = 10.0 ± 0.98 mM, K
m d-glucose = 6.0 ± 0.64 mM, K
i d-glucose = 8.5 ± 0.81 mM. |
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Keywords: | Candida rugosa lipase Competitive substrate inhibition Dead-end lipase– substrate complex d-Glucose" target="_blank">d-Glucose l-Phenylalanine" target="_blank">l-Phenylalanine Ping-Pong Bi-Bi mechanism Rhizomucor miehei lipase |
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