Active enzyme coupling with

Kim Y-S, Kara M, Ikebukuro K, Miyake J, Ohkawa H, Karube 1 (1996) Photo-induced activation of cytochrome P450/reductase fusion enzyme coupled with spinach chloroplasts. Biotechnol Tech 10 717-720... 

Most of us anticipated that ribosyl activation for nucleotide biosynthesis would use the same device of phosphorylation, so well known for glucose. But the novelty of pyrophos-phorylation used by this enzyme (coupled with elimination of inorganic pyrophosphate upon subsequent condensations) established my unalloyed awe for the ingenuity and fitness of an enzyme. 

Specificity for a particular charged substrate can be engineered into an enzyme by replacement of residues within the enzyme-active site to achieve electrostatic complementarity between the enzyme and substrate (75). Protein engineering, when coupled with detailed stmctural information, is a powerful technique that can be used to alter the catalytic activity of an enzyme in a predictable fashion. 

The oxidation of heteroatoms and, in particular, the conversion of sulfides to asymmetric sulfoxides has continued to be a highly active field in biocatalysis. In particular, the diverse biotransformations at sulfur have received the majority of attention in the area of enzyme-mediated heteroatom oxidation. This is particularly due to the versatile applicability of sulfoxides as chiral auxiliaries in a variety of transformations coupled with facile protocols for the ultimate removal [187]. 

The final method of coupling enzyme reactions to electrochemistry is to immobilize an enzyme directly at the electrode surface. Enzyme electrodes provide the advantages already discussed for immobilization of enzymes. In addition, the transport of enzyme product from the enzyme active site to the electrode surface is greatly enhanced when the enzyme is very near to the electrode. The concept of combining an enzyme reaction with an amperometric probe should offer all of the advantages discussed earlier for ion-selective (potentiometric) electrodes with a much higher sensitivity. In addition, since the response of amperometric electrodes is linear, background can be selected. 

Chohnesterase-inhibiting pesticides (e g., organophosphate and carbamate pesticides) are detected by dipping the developed chromatogram in a solution of the enzyme chohnesterase followed by incubation for a short period. Then the plate is dipped in a substrate solution, e.g., 1-naphthyl acetate/fast blue salt B. In the presence of the active enzyme, 1-naphthyl acetate is hydrolyzed to 1-naphthol and acetic acid, and the 1-naphthol is coupled with fast blue salt B to form a violet-blue azo dye. The enzyme is inhibited by the pesticide zones, so the enzyme-substrate reaction does not occur pesticides are, therefore, detected as colorless zones on a violet-blue background [36]. 

A marked interference with heme synthesis results in a reduction of the hemoglobin concentration in blood. Decreased hemoglobin production, coupled with an increase in erythrocyte destruction, results in a hypochromic, normocytic anemia with associated reticulocytosis. Decreased hemoglobin and anemia have been observed in lead workers and in children with prolonged exposure at higher PbB levels than those noted as threshold levels for inhibition or stimulation of enzyme activities involved in heme synthesis (EPA 1986a). 

Methods similar to those discussed in this chapter have been applied to determine free energies of activation in enzyme kinetics and quantum effects on proton transport. They hold promise to be coupled with QM/MM and ab initio simulations to compute accurate estimates of nulcear quantum effects on rate constants in TST and proton transport rates through membranes. 

The catalytic activity of CYP enzymes requires functional coupling with its redox partners, cytochrome P450 NADPH oxidoreductase (OR) and cytochrome bs. Measurable levels of these two proteins are natively expressed in most cell lines. Therefore, introduction of only the CYP cDNA is generally needed for detectable catalytic activity. However, the levels of expression of the redox partner proteins may not support maximal CYP catalytic activity, and therefore enhancement of OR levels may be desirable. This approach has been used successfully with an adenovirus expression system in LLC-PKi cells [12],... 

Figure 20.3 The reaction of SMCC with the amine groups on enzyme molecules yields a maleimide-activated derivative capable of coupling with sulfhydryl-containing antibody molecules.

The amine groups on these fragments also may be modified with thiolating agents, such as SATA or 2-iminothiolane, to create sulfhydryl residues suitable for coupling to maleimide-activated enzymes (Section 1.1, this chapter) (Figure 20.13). Amine groups further may be utilized... 

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