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Methylated Derivatives of L-tyrosine in Reaction Catalyzed by L-amino Acid Oxidase: Isotope and Inhibitory Effects

Methylated Derivatives of L-tyrosine in Reaction Catalyzed by L-amino Acid Oxidase: Isotope and Inhibitory Effects

Małgorzata Pająk

J Biochem. 2020 Jun 22;mvaa066.

PMID: 32569353

Abstract:

L-Amino acid oxidase is widely distributed in nature and shows important biological activity. It induces cell apoptosis and has antibacterial properties. The present study was designed to investigate the effect of methyl substituent on its activity as methylated derivatives of L-tyrosine, labelled with short-lived B+ emitters have been used in oncological diagnostics. To study isotope effects in the oxidative deamination of O-methyl-L-tyrosine the deuterated isotopomer, i.e. O-methyl-[2-2H]-L-tyrosine was synthesized by isotope exchange, catalyzed enzymatically by tryptophanase. Isotope effects were determined using the spectrophotometric non-competitive method. The values of isotope effects indicate that the α-C-H bond cleavage occurs in the rate determining step of the investigated reaction and α-hydrogen plays a role in the substrate binding process at the enzyme active site. The inhibitory effect on L-amino acid oxidase activity was studied with α-methyl-L-tyrosine and N-methyl-L-tyrosine. The mode of inhibition was determined based on Lineweavear-Burk plots intersections. α-Methyl-L-tyrosine has been found a mixed type inhibitor of the investigated enzyme, while N-methyl-L-tyrosine is a non-competitive inhibitor of L-amino acid oxidase.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP672877-B	α-Methyl-L-tyrosine		672-87-7	Price

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