Enzyme bridge complexes

Synthesis of functional models of carbonic anhydrase has been attempted with the isolation of an initial mononuclear zinc hydroxide complex with the ligand hydrotris(3-t-butyl-5-methyl-pyrazolyl)borate. Vahrenkamp and co-workers demonstrate the functional as well as the structural analogy to the enzyme carbonic anhydrase. A reversible uptake of carbon dioxide was observed, although the unstable bicarbonate complex rapidly forms a dinuclear bridged complex. In addition, coordinated carbonate esters have been formed and hydrolyzed, and inhibition by small ions noted.462 A number of related complexes are discussed in the earlier Section 6.8.4. 

Various alkane oxidations are catalyzed by iron complexes. Such reactions are important in view of the action of non-heme iron enzymes, such as methane monooxygenase, in hydrocarbon oxidations in biological systems. For example, the oxo-bridged complex [Fe2(TPA)2(ju,-0)(ju.-0Ac)]3+ [TPA = tris(2-pyridylmethyl)-amine] catalyzes the oxidation of cyclohexane with Bu OOH. Related complexes with an Fein2(/i-0)(/i-0Ac)2 core oxidize cyclohexane or adamantane to give a mixture of alcohols and ketones.159 Less well defined systems, e.g., FeCl3-6H20/ aldehyde/AcOH/02 are similarly active.160... 

The locations of the following functional groups around the N-terminal Thr-1 of the bovine p7 subunit are consistent with the structure of an Ntn-hydrolase-active site (Fig. 3.4A). The N-terminal Thr-1 forms a hydrogen bond with Asn-104 0<5. Thr-1 Oy-H forms a hydrogen bond with Asp-59 0.<5 Arg-91 of p forms a salt bridge with Asp-56 of pi. An oxyanion hole is formed by the Tyr-88 OHof pi or Arg-99 N / of p7. A water molecule is found near Thr-1 and is replaced by substrate upon formation of the enzyme-substrate complex (Fig. 3.4 B). Although the... 

Fluorouracil is widely used in cancer chemotherapy. It is a precursor of 5-fluoro-dUMP, which is a mechanism-dependent inhibitor of thymidylate synthetase. It forms a stable methylene-bridged complex with methylene-tetrahydrofolate on the enzyme catalytic site that cannot undergo reductive cleavage. 

The use of immunologically linked enzyme-antibody complexes will most probably increase due to the advent of monoclonal antibodies. The preparation of such complexes is not only extremely simple (Section 11.3.2), but can be done with crude enzyme extracts. A bridging antibody (ABii k) is needed to link the enzyme-antibody complex (Ab E) to the primary antibody (Ablest) ... 

Apply the bridging molecule and the enzyme-antibody complexes, as determined in Table 14.3A. steps 2 and 3. 

Antibody-masking enzyme tag immunoassay Adenosine 5 -monophosphate S-Acetylmercaptosuccinic anhydride Alkaline phosphatase anti-alkaline phosphatase (enzyme-antibody) complex Alkaline phosphatase 5-Aminosalicylic acid Adenosine 5 -triphosphate Aa-Benzoyl-L-arginine ethyl ester (-f-)-Biotin bromoacetyl hydrazide (-b)-Biotin Y-aminocaproic acid A-hydroxy-succinimide ester Bis-diazotized benzidine -Galactosidase (-I- )-Biotin hydrazide (-I- )-Biotin-A-hydroxysuccinimide ester (-I-)-Biotin p-nitrophenyl ester Bridged avidin-biotin (method)... 

Villafranca, J, J., Mildvan, A. S. The Mechanism of Aconitase Action, III. Detection and Properties of Enzyme — Metal — Substate and Enzyme — Metal — Inhibitor Bridge Complexes with Manganese (II) and Iron (II). J. Biol. Chem. 247, 3454 (1972). 

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