Inactivation of chosen dehydrogenases by the products of water radiolysis and secondary albumin and haemoglobin radicals.
OBJECTIVE
Inactivation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH) by products of water radiolysis and by secondary radicals localized on haemoglobin (Hb) and human albumin (HSA) was studied.


METHODS
Aqueous solutions of ADH, GAPDH and LDH were irradiated under air and under nitrous oxide (N2O) in the absence and in the presence of Hb or HSA. In order to determine the effectiveness of inactivation of the enzymes by radicals localized on Hb and HSA, the inactivation efficiency determined experimentally was compared with that calculated under assumption that only hydroxyl radicals are responsible for the enzyme inactivation.


RESULTS
In the absence of other proteins, under air, GAPDH showed the highest radiation sensitivity, followed by ADH and LDH. The sequence was reverse under anaerobic atmosphere. Oxygen increased considerably the inactivation of GAPDH and ADH. Secondary albumin and haemoglobin radicals brought about considerable inactivation of GAPGH and ADH. Albumin radicals (HSA) generated under N2O inactivated GAPDH and ADH more effectively than haemoglobin radicals (Hb). Under air, however, inactivation of GAPDH and ADH by haemoglobin peroxyl radicals was higher than by albumin peroxyl radicals. LDH was resistant to inactivation by haemoglobin and albumin radicals, and peroxides of these proteins.


CONCLUSIONS
In the light of these results and literature data, the observed differences in the effectiveness of inactivation of the dehydrogenases studied by secondary protein radicals depend on the amino acid residues present at the active site and in its close neighborhood and on the number of amino acid residues available on the protein surface.
Kowalczyk
Aleksandra
A
Department of Molecular Biophysics, University of Lódź, Lódź, Poland. olakow@biol.uni.lodz.pl
Serafin
Eligiusz
E
Puchała
Mieczysław
M
D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000528:radiation effects; D005609:Free Radicals / Q000737:chemistry / Q000528:radiation effects; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000528:radiation effects; D006454:Hemoglobins / Q000528:radiation effects*; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000528:radiation effects; D009609:Nitrous Oxide / Q000737:chemistry; D010088:Oxidoreductases / Q000737:chemistry / Q000528:radiation effects*; D010100:Oxygen / Q000737:chemistry; D012709:Serum Albumin / Q000737:chemistry / Q000528:radiation effects*; D014867:Water / Q000737:chemistry*
D005609:Free Radicals; D006454:Hemoglobins; D012709:Serum Albumin; D014867:Water; D010088:Oxidoreductases; D000426:Alcohol Dehydrogenase; D007770:L-Lactate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D009609:Nitrous Oxide; D010100:Oxygen