Experimental studies on the quality of food proteins

The role of elongation factors in protein synthesis rate variation in white teleost muscle

Protein synthesis-stimulating activity was assayed in the cytosolic fraction of white muscle from teleost fish (rainbow trout, carp) and of rat liver. In vitro protein synthesis-stimulating activity in the cytosolic fraction is reduced by food deprivation. The addition of elongation factors EF1, EF2, or EF1 + EF2 compensates for the starvation-induced loss of protein synthesis-stimulating activity in trout muscle cytosol. The action of EF2 is stronger than that of EF1 in this respect. However, EF1 enhances in vitro protein synthesis-stimulating activity in rat liver cytosol more than EF2. The EF2 concentration in the cytosolic fraction of white muscle from starved trout is significantly lower than in fed specimens.

[The effect of the nutritional status of rats on the protein biosynthetic activity in a cell-free system]

The recent paper deals with the influence of nutritional situation on the ability of cell sap fractions of liver and muscle of rats to stimulate protein biosynthesis in a cell-free system. The incorporation of 3H-leucine into polypeptides from tissues of ad libitum fed rats was 1.25-1.46 fold higher in the liver resp. 1.2-1.7 fold higher in the muscle in comparison to the incorporation data of the starved rats. Significant differences were also shown in the course of translation (incorporation of amino acids in dependence of concentration and time). The amino acid incorporation of starved animals rapidly reached a plateau at a low level of incorporation (liver 40,000 dpm, muscle 9,000 dpm) whereas at higher cell sap concentrations and prolonged times of incubation (120 min) degradation effects (proteolysis) must be taken into account. The incorporation of amino acids in tissues of ad libitum fed animals has still increased under the same conditions (liver 55,000 dpm, muscle 16,000 dpm). These results obtained with in-vitro-methods confirm findings got with in-vivo-techniques and may complete the investigations of protein metabolism sensibly.