Accession Number : AD0730825

Title :   Effects of X-Irradiation on the Various Enzymic Functions of NADP(+)-Linked Isocitrate Dehydrogenase,

Corporate Author : MEMORIAL UNIV OF NEWFOUNDLAND ST JOHN'S DEPT OF BIOCHEMISTRY

Personal Author(s) : Holland,Peggy ; Little,Clive

Report Date : 13 NOV 1970

Pagination or Media Count : 7

Abstract : Highly puridied NADP(+)-linked isocitrate dehydrogenase was X-irradiated in dilute aqueous solution and proved to be very radiosensitive, being inactivated with a G value of 0.5. The catalytic functions of the enzyme were destroyed at the same rate. However, unlike most allosteric enzymes, the allosteric properties were not more radiosensitive than the catalytic properties. X-ray inactivation was associated with the destruction of seven to eight sulfhydryl groups. The first four sulfhydryls destroyed were extremely radiosensitive, having G values for destruction of almost 2. Comparison with several reagents known to attack sulfhydryl groups suggested that sulfhydryl destruction was sufficient to account for the X-ray response pf the enzyme. Destruction of the single essential methionine did not seem significant in the inactivation. X-ray inactivation was also associated with increases in the K(m) values for isocitrate and manganese. (Author)

Descriptors :   (*RADIATION EFFECTS, *ENZYMES), X RAYS, IN VITRO ANALYSIS, OXIDOREDUCTASES, THIOLS, CANADA, REACTION KINETICS

Subject Categories : Biochemistry
      Radiobiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE