Methionine selective enzyme electrode

Assay method for antitumor l-methionine γ-lyase: comprehensive kinetic analysis of the complex reaction with l-methionine

“…Fung et al [17] described a potentiometric enzyme electrode prepared with immobilized METase for the assay of L L -methionine. Tanaka et al [18] demonstrated a method of selective determination of L L -methionine and L L -cysteine using METase and they [19] also described the synthesis of D D -a-aminobutyrate using both METase and D D -amino acid aminotransferase.…”

On-line gas dialyzer for automated enzymatic analysis with potentiometric ammonia detection

“…Potentiometric gas sensors, particularly the ammonia gas sensor, have become useful analytical detectors for the determination of amino acids and other biomolecules (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). In these assay systems, various biocatalysts (e.g., enzymes, bacterial cells or tissue slices) are either immobilized on the surface of the gas sensor's membrane (1)(2)(3)(4)(5)(6)(7)(8) or, as in a flowthrough arrangement, the biocatalysts are used in soluble form or are immobilized in a tubular reactor (9)(10)(11). These biocatalysts serve to selectively convert the biomolecule to ammonia (so called "deaminase" enzymes).…”

“…However, if there is any delay in the analysis of the sample, these background NH3-N levels will greatly increase due to the hydrolysis of blood components into ammonia (14). This increase in NH3-N can interfere with the accuracy of the 1 Present address: Polaroid Corp., 750 Main St., Cambridge, MA 02139. assay. Consequently, physiological samples have to be pretreated by various tedious and time-consuming methods such as cation exchange (11,15) or alkalinization followed by heat evaporation (16,17).…”

Biosensors for environmental control

“…An ammonia gas electrode consisting of a combined glass electrode and a gas permeable membrane is usually used for this purpose(ref. 8,9). In this case, the determination must be performed under strong alkaline conditions (above pH 11).…”