Effects of starvation, hyperproteic diet and nicotinamide treatment on the L-threonine aldolase and allothreonine aldolase of rat liver [Effetto del digiuno, della dieta iperproteica e del trattamento con nicotinamide sulla treonina e allotreonina aldolasi di fegato di ratto]

In order to evaluate if the aminoacid L-threonine and its isomer allothreonine are metabolized by a single protein or by two specific enzymatic proteins, in the rat liver, we have studied the behaviour of L-threonine aldolase activity and allothreonine aldolase activity in rats which are injected with nicotinamide (1 g/ Kg) or have received a special diet containing 91% of casein or that have been starved for several days. The L-threonine aldolase enhances its activity in all three cases, while the allothreonine aldolase does not show significative changes of activity. These different behaviours of the two enzymatic activities, support the hypothesis that in the rat liver two proteins are necessary for the metabolism of the L-threonine and its isomer allothreonine.