Enzyme oxalate oxidase

Why is the operational stability of an enzyme-based thermal sensor for oxalic acid expected to be poorer than an amperometric oxalate sensor prepared using the same enzyme, oxalate oxidase ... 

Lahrou NE, Clonis YD. Biomimetic dye-ligand for oxalate requiring enzymes Studies with oxalate oxidase and oxalate decarboxylase. J Biochem 1995 40 59. 

Assolant-Vinet and Coulet (1986) used a preactivated Biodyne Im-munoaffinity Membrane (Pall, USA) to cover two electrodes working in differential mode. Immobilization was performed by simply dropping the enzyme solution onto the membrane, i.e., the biosensor-users may prepare the enzyme membranes themselves. Good results were obtained with GOD, lactate oxidase, and oxalate oxidase (Coulet, 1987). 

Determination of oxalate with immobilized oxalate oxidase in an enzyme thermistor Anal. Lett. 18 573-88... 

Other examples of amperometric enzyme electrodes based on the measurement of oxygen or hydrogen peroxide include electrodes for the measurement of galactose in blood (galactose oxidase,enzyme), oxalate in urine (oxalate oxidase), and cholesterol in blood serum (cholesterol oxidase). Ethanol is determined by reacting with a cofactor, nicotinamide adenine dinucleotide (NAD" ) in the presence of the enzyme alcohol dehydrogenase to produce the reduced form of NAD", NADH, which is electrochemically oxidized. Lactate in blood is similarly determined (lactate dehydrogenase enzyme). 

The recently published structure of this dimeric enzyme that contains one type II Cu(II) catalytic center per monomer has revealed that it belongs to the cupin superfamily, that includes Fe-homogentisate 1,2-dioxygenase and Mn-oxalate oxidase, enzymes which are evolutionary related, in spite of their different metal preferences (4). The crystal structure shows that the Cu ion has two different coordinations. The first coordination environment, which represents approxi-... 

Oxalic acid poses a problem to both leafy plants and vertebrates because these organisms cannot catabolize it [108]. Although accumulation of oxalate leads to stress in plants, in vertebrates this molecule can be metaboHzed by bacteria present in the intestinal tract [109]. Oxalate can be catabolized in different ways by oxidation, by decarboxylation of oxalyl-coenzyme A or by direct decarboxylation. Both oxidation and decarboxylation of oxalate are catalyzed by Mn-containing enzymes. Here we will discuss the oxalate decarboxylate reaction that produces formate and CO2. The crystal structure of oxalate oxidase from Bacillus subtilis... 

Oxalate Oxidase. For the oxalate oxidase system, the value of the Michaelis constant (Km) increased for the sol-gel nanoconfined system (Km /lO = 1.1 in solution and 4.1 in aged gel). The approximately fourfold increase indicates that the binding of the oxalate with the enzyme is weaker. The apparent association constant (kcat/ m) for the oxalate-oxalate oxidase complex was substantially altered as a result of confinement of the protein the sol-gel matrix (kcat/Km = 170 in solution and 2.3 in aged gel). This implicates a relatively destabilized enzyme-substrate complex. Additionally, the kcat parameter is also reduced in the gel (kcat /lO" = 187 in solution and 9.4 in aged gel), suggesting deactivation of the product forming step in the gel medium. In this case, whole the dissociative product forming step is reduced only by a factor of 20 (187/9.4), the associative step is reduced considerably by a factor of 75 (170/2.3). 

Kotsira, V. P. Clonis, Y. D. (1998). Chemical Modification of Barley Root Oxalate Oxidase Shows the Presence of a Lysine, a Carboxylate, and Disulfides, Essential for Enzyme Activity. Archives Biochem Biophys., 356, 117-126. 

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

Hydrogen peroxide produced as a result of reactions of oxidase enzymes with analyte substrates can be sensitively determined, both directly by luminol ECL and indirectly by Ru(bpy)32+ ECL. For the latter, hydrogen peroxide is detected on the basis of its ability to diminish the ECL reaction between Ru(bpy)32+ and added oxalate, by reacting with, and depleting the concentration of, oxalate. Thus ECL intensity is inversely proportional to the concentration of analyte. This principle has been used, for example, to determine cholesterol [70],... 

A6. Arakawa, H., Maeda, M., and Tsuji, A., Chemiluminescence enzyme immunoassay of 17a-hydroxyprogesterone using glucose oxidase and bis(2,4,6-trichlorophenyl) oxalate-fluorescent dye system. Chem. Pharm. Bull. 30, 3036-3039 (1982). 

The activity of the enzyme is also strongly affected by the presence of inhibitors. Fluoride ions inhibit urease (173) and oxalate ions inhibit lactate oxidase (174), but the major inhibitors are heavy-metal ions, such as Ag+, Hg +, Cu " ", organophosphates, and sulfhydryl reagents (/i-chloromercuribenzoate and phenylmercury(II) acetate), which block the free thiol groups of many enzyme active centers, especially oxidase (69). Inhibiting the enzyme electrodes makes it possible to quantify the inhibitors themselves (69), for example, H2S and HCN detection using a cytochrome oxidase immobilized electrode (176). 

Allopurinol (e.g., Zyloprim) Decreases uric acid levels by inhibiting xanthine oxidase, the enzyme which converts hypoxanthine to xanthine and xanthine to uric acid. Tophaceous gout, recurrent calcium oxalate stones. May exacerbate gout attacks. GI upset, hepatotoxicity, rash, Stevens-Johnson syndrome. ... 

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