Depression of Substrate Inhibition in Gamma Irradiated Lactic Dehydrogenase

Journal Article · Thu Nov 01 04:00:00 EST 1973 · Radiation Research

DOI:https://doi.org/10.2307/3573670· OSTI ID:4389947

Saito, Masahiro

Dilute solutions of chicken heart lactic dehydrogenase were exposed to ⁶⁰Co gamma irradiation. The dose effect curve varied in shape depending on the pyruvate concentration used in the assay of LDH activity. At a lower concentration of pyruvate, the LDH activity decreased exponentially with the dose. However, at an excess concentration of pyruvate, the residual LDH activity initially increased with increasing dose before a loss in activity was observed. The S- V plot of irradiated LDH showed that the substrate inhibition of chicken heart LDH at excess pyruvate concentration was oonsiderably depressed by gamma irradiation. The mechanism of the decreased substrate inhibition was studied by examining the formation of an abortive ternary complex of the type pyruvate-NAD- LDH upon incubation of LDH with pyruvate and NAD. The result shows that irradiation decreases the formation of the abortive ternary complex, resulting in the release from substrate inhibition.

• Research Organization: Kyoto Univ.
• Sponsoring Organization: USDOE
• NSA Number: NSA-29-005281
• OSTI ID: 4389947
• Journal Information: Radiation Research, Journal Name: Radiation Research Journal Issue: 2 Vol. 56; ISSN 0033-7587
• Publisher: Radiation Research Society
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*LACTATE DEHYDROGENASE-- METABOLISM
BIOCHEMICAL REACTION KINETICS
CATALYSIS
GAMMA RADIATION
HEART
INHIBITION
N48110* --Life Sciences--Radiation Effects on Biochemicals-- In-Vitro
PHOTON BEAMS
PYRUVIC ACID
RADIATION DOSES