Usefulness of Kinetic Enzyme Parameters in Biotechnological Practice

Abstract

The kcat /KM ratio, where kcat is the catalytic constant for the conversion of substrate into product, and KM is the Michaelis constant, has been widely used as a measure of enzyme performance, but recent analyses have underscored the inadequacy of this ratio to describe the efficiency of a biocatalyst, particularly when employed as a criterion for selecting between enzyme variants for industrial purposes. The main problem with this kinetic relationship is that it neglects the contribution of important factors operating in actual bioprocess conditions, such as substrate concentrations and product inhibition, leading to unreal expectations on enzyme performance and erroneous selection of the most adequate biocatalyst. Two complementary formalisms, the efficiency function and the catalytic effectiveness, have been introduced to incorporate important features of any bio-industrial system. We review herein the rationales underlying each derivation, and the strengths and fields of application of both strategies. Examples of different situations, including continuous and batch-type reactors, as well as reversible and irreversible processes, are provided, together with recommendations on the use of both approaches.

Functional specialization of UDP‐glycosyltransferase 73P12 in licorice to produce a sweet triterpenoid saponin, glycyrrhizin

“…Notably, the K m app and k cat app values, which were calculated in the presence of one original sugar donor substrate and another potential competitive sugar donor, were markedly decreased when compared with the K m and k cat values only in the presence of the original sugar donor substrate. The difference between the k cat app / K m app and k cat / K m ratios was not considered here because of the large difference between the K m app and K m values and the resultant usage limit of the k cat app / K m app ratio, as previously described (Koshland, ; Eisenthal et al ., ; Carrillo et al ., ). The reduction of the K m app and k cat app values indicates mixed or uncompetitive inhibition of UGT73P12 protein activity by the potential competitive sugar donor.…”

Citraconylation and maleylation on the catalytic and thermodynamic properties of raw starch saccharifying amylase from Aspergillus carbonarius

“…From Table 2 , it appears that the native amylase has better catalytic efficiency (Kcat/Km) compared to the CAM and MAM. However, reports have shown that the use of Kcat/Km, to evaluate catalytic efficiency is often misleading, and does not hold when the enzyme operates under high substrate condition which is often obtainable under industrial conditions where the enzymes are applied for biotechnological purposes [ 43 ]. Liu and co-workers [ 20 ] while evaluating the kinetic constants of horseradish peroxidase treatment on the dyes, bromophenol blue and methyl orange reported that citraconic anhydride-modified horseradish peroxidase had a greater affinity and catalytic efficiency compared to the native enzyme.…”

gp120 Alters Its Conformation to Enhance Evasiveness and Infectivity

“…The gp120 molecule directly interacts with CD4 during receptor-ligand interactions that lead to receptor binding (109). Some studies have reported that the antibody interacting surface undergoes significant dynamic motion, as "if fastening to gp120 and wrenching it" (Néstor et al, 2010). The receptor might have employed these conformation adjustments to tightly bind to its ligand.…”