Non-productive binding

A frequent case in enzyme kinetics is the ability of enzymes to form numerous non-productive complexes with substrates, that do not break down (Fersht, 1999). If an enzyme molecule binds a single substrate molecule in a productive complex EA, but also another substrate molecule in a non-productive complex AE, we are referring to non-productive binding of this substrate. Akinetic model is analogous to that for a linear competitive inhibition (Section 5.2). 

the Michaelis-Menten equation is obeyed exactly for this mechanism and so the observed double reciprocal plot does not indicate whether the non-productive binding is significant or not. Since, in this case, the true V ax is deaeased by a factor (i+JTA/ i)i and is not affected, it is always advisable to be aware of it when interpreting results for several substrates of an unspecific enzyme. 

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Despite a higher intrinsic reactivity, epoxides of type 35 and 36 show a lower inactivation rate kj(max), as seen in Table XI, than the conduritol epoxides. This is probably caused by the greater flexibility of the epoxyalkyl chain in the active-site cleft, and by non-productive binding in positions where the oxirane is not within reach of the catalytic groups of the active site. For epoxypropyl oligosaccharides, this would hold even when the inhibitor occupies the correct subsites. 

An unavoidable limitation of Kelly s host was that the two binding sites were identical, which allowed non-productive binding of two identical substrates. Kelly therefore designed a new receptor with two different binding motifs that selectively... 

The substrate binding pocket of horse liver alcohol dehydrogenase comprises residues from both subunits (Fig. 26B) [123]. The active site is shown in Fig. 27, with NAD(H) bound, and p-bromobenzyl alcohol bound in a non-productive binding mode. The hydrophobic residues (from both subunits) that line the substrate binding... 

T " 27. The active site of horse liver alcohol dehydrogenase, with bound NAD(H) and a non-productive binding mode of p-bromobenzyl alcohol. The... 

Michaelis-Menten equations often do not apply for enzymatic reactions at surfaces, such as bacterial walls (McLaren and Packer, 1970). Precise kinetic parameters, which can only be obtained with well-characterized low molecular weight substrates, are complicated by non-productive binding of small substrates, i.e. binding outside of the catalytic site. 

Daniels-Holgate, P.U. and Dolly, J.O. 1996. Productive and non-productive binding of botulinum neurotoxin A to motor nerve endings are distinguished by its heavy chain. J. Neurosci. Res. 44 263-271. 

C. W. Wharton, A. Comish-Bowden, K. Brocklehurst, and E. M. Crook. Kinetics of the hydrolysis of N-benzoyl-L-serine methyl ester catalysed by bromelain and by papain. Analysis of modifier mechanisms by lattice nomography, computational methods of parameter evaluation for substrate-activated catalyses and consequences of postulated non-productive binding in bromelain- and papain-catalysed hydrolysis. Biochem. J. 141 365 (1974). 

Competitive inhibition of lysozyme by potential oligosaccharide substrates has been explained as being caused by their non-productive binding at sites adjacent to, but not across, the bond-breaking site (24). The inhibition of certain 0-1,4-glucan endo-hydrolases by cellobiose and lactose (138) may have an analogous physical explanation. 

Non-productive binding is sometimes suggested to account for the low reactivity of poor substrates by suggesting that they bind at sites on the enzyme where the catalytic reaction cannot take place. 

The non-productive binding of the substrate resulting in the formation of the ES inactive complex according to the scheme... 

Productive binding of the substrate by the enzyme appears in the cases where the improvement of complex formation in the substrate series (decrease in the substrate constant) either increases the maximum transformation rate or has no effect on this rate. Opposite effects are observed for non-productive binding. 

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