Artificial enzymes product inhibition

Product inhibition and substrate inhibition are effects also known in enzyme catalysis that can reduce catalytic efficiency. Generally, catalytic systems (natural or artificial) based on covalent interactions are more sensitive towards inhibitions than non-covalent systems utilizing weak interactions Garcia-Junceda, E. (2008) Multi-Step Enzyme Catalysis, Wiley-VCH Verlag GmbH, Weinheim, Germany. 

Enzymes are proteins that catalyze reactions. Thousands of enzymes have been classified and there is no clear limit as to the number that exists in nature or that can be created artificially. Enzymes have one or more catalytic sites that are similar in principle to the active sites on a solid catalyst that are discussed in Chapter 10, but there are major differences in the nature of the sites and in the nature of the reactions they catalyze. Mass transport to the active site of an enzyme is usually done in the liquid phase. Reaction rates in moles per volume per time are several orders of magnitude lower than rates typical of solid-catalyzed gas reactions. Optimal temperatures for enzymatic reactions span the range typical of living organisms, from about 4°C for cold-water fish, to about 40°C for birds and mammals, to over 100°C for thermophilic bacteria. Enzymatic reactions require very specific molecular orientations before they can proceed. As compensation for the lower reaction rates, enzymatic reactions are highly selective. They often require specific stereoisomers as the reactant (termed the substrate in the jargon of biochemistry) and can generate stereospecific products. Enzymes are subject to inhibition and deactivation like other forms of catalysis. 

One of the most important challenges of development of artificial enzymes is product inhibition, which prevents a catalytic turnover or decreases the reaction... 

After haemodialysis, heat production showed a further increase (Table 29), presumably due to heparinization. Heparin is used as an anticoagulant to inhibit blood clotting during extracorporeal circulation of blood in the artificial kidney. Heparin is known to release enzymes, such as lipases and diamino oxidases, into the circulation. Thereby exothermic chemical reactions are expected to be induced in the plasma. On the other hand, oxygen consumption decreased significantly after haemodialysis, probably due to removal of oxygen-consuming substances. 

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