Evaluations of tyrosine apodecarboxylase assays for pyridoxal phosphate

Conference · Thu May 01 04:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5272425

Fonda, M L

The alternate procedures used in the tyrosine apodecarboxylase assays for pyridoxal 5'-phosphate were evaluated to determine optimal conditions. Two preparations of tyrosine apodecarboxylase from S. faecalis were used: a cell suspension and a partially purified cell-free form. The activity of the decarboxylase was measured in two different assays using (/sup 14/C)tyrosine or (/sup 3/H)tyrosine as substrate. The presence of serum proteins inhibited both assays for serum pyridoxal-P; since a higher concentration of serum was used in the (/sup 14/C)-tyrosine assay, that assay was inhibited to a greater extent. In contrast, addition of deproteinized serum extract did not appear to inhibit either assay. The rate of reconstitution of the apodecarboxylase in the cell suspension was at least four times slower than that of the cell-free enzyme. The rate of reconstitution of the cell-free enzyme was faster in acetate than in citrate buffer. Inorganic sulfate or phosphate, at normal plasma concentrations, did not alter either the reconstitution rate of tyrosine decarboxylase or the final activity obtained in the assays using either substrate. The tyrosine apodecarboxylase assay for pyridoxal-P can be optimized by using deproteinized sera or plasma and incubating the cell-free apoenzyme with the coenzyme in acetate buffer for sufficient time to obtain maximum reconstitution.

• Research Organization: Univ. of Louisville School of Medicine, KY
• OSTI ID: 5272425
• Report Number(s): CONF-8606151-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:6
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
CARBON 14 COMPOUNDS
CARBON-CARBON LYASES
CARBOXY-LYASES
CARBOXYLASE
CARBOXYLIC ACIDS
ENZYME ACTIVITY
ENZYMES
HYDROXY ACIDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LYASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
RADIOENZYMATIC ASSAY
SUBSTRATES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TYROSINE