Lysine alpha-ketoglutarate reductase and lysine oxidation are distributed in the extrahepatic tissues of chickens.

In animals, lysine oxidation is thought to occur primarily via the activity of lysine alpha-ketoglutarate reductase (LKR). This activity was reported previously in chicken liver, but no work on the tissue distribution of the enzyme in chickens has been reported. Therefore, LKR activity was assayed in liver, kidney, pancreas, heart, brain, lung, spleen, muscle, and intestinal tissues in chickens as was the in vitro ability of tissue homogenates to oxidize lysine. Additionally, the expression of LKR mRNA was assessed by RT-PCR. We found LKR to be present in all tissues studied by both enzymatic analysis and mRNA abundance. Additionally, all tissues assayed oxidized lysine. The extent of lysine oxidation differed among the tissues, consistent with the different pathways of lysine oxidation in the different tissues. These studies demonstrate that LKR is widely distributed in chicken tissues and that tissues other than liver can contribute to whole-body lysine oxidation.