The modified base
queuine is a nutrient factor for lower and higher eukaryotes except yeast. It is synthesized in eubacteria and inserted into the wobble position of specific tRNAs (
tRNA(GUN)) in exchange of
guanine at position 34. The tRNAs of Q family are completely modified in terminally differentiated somatic cells. However, mainly free
queuine is present in embryonic and fast proliferating cells,
tRNA remains Q deficient.
Lactate dehydrogenase (
LDH) A mRNA and
LDH A protein is known to increase when cells are grown in hypoxic conditions. In the present study, the level of LDH
isozymes is analyzed in different tissues of normal and cancerous (DLA) mice and the effect of
queuine treatment on LDH
isozyme is observed.
LDH A isozyme is shown to increase in serum and liver of DLA mice. The level and activity of
LDH A decreases on
queuine treatment. In skeletal muscle and heart,
LDH A isozyme decreases while
LDH B increases in DLA mice.
Queuine administration leads to change back towards normal. In case of brain,
LDH A increases but
LDH B decreases in DLA mice.
Queuine treatment leads to decrease in A4 anaerobic
isozymes of LDH. The results suggest that
queuine suppresses anaerobic glycolytic pathway, which leads to
tumor suppression of DLA mice.