Some AA and its levels and forms also affect the degradation of proteins in liver and muscle. The degradation of tissue protein is mainly carried out by two ways: cytolysosome and non lysosome. Lysosomal pathway generally accounts for 60% - 90% of the total degradation according to the nutritional status of animals (seglen et al., 1979), and when AA is exhausted, it accounts for 50% of the total degradation (khairallah, 1985; FURUNO et al., 1986);

Henell et al., 1987; bebevenga et al., 1993). However, when starvation or insufficient intake of AA, liver autolysis and protein degradation speed were accelerated;

Parenteral nutrition test showed that different levels of AA supply mainly affected turnover metabolism by controlling protein degradation in rat liver (Chiku, 1993). Although a large number of studies have tried to find AA that interferes with the proteolysis pathway, it is still unclear which AA is responsible for preventing this process. At present, it is believed that the AA that has the effect of inhibiting proteolysis mainly includes tryptophan (Hopgood et al., 1977;

Sommercohen et al., 1981; grinde, 1984), leucine (sommercohen et al., 198l), and methionine (sommercohen et al., 1981; Mortimore et al., 1988). Mortimore et al. Suggested that leucine, tyrosine, glutamic acid, proline, histidine, tryptophan and methionine together inhibit the autolysis of proteins, and alanine may play an auxiliary regulatory role (Mortimore et al., 1987; 1988).

The regulation of muscle protein degradation is the same as that of liver. AA depletion can promote lysosomal pathway, while insulin can inhibit this process (buse et al., 1975; fulks et al., 1975). The non lysosomal pathway is mainly promoted by Ca2 +, which is mainly responsible for protein hydrolysis in pathological state.

In AA, branched chain AA, especially leucine, can effectively inhibit the degradation of skeletal muscle and myocardial proteins (buse et al., 1975; fulks et al., l975; Li et al., 1978; Chua et al., 1979). However, in some conditions, it was found that leucine content in muscle did not decrease but increased with the increase of protein hydrolysis (milewski et al., 1982), indicating that leucine may not participate in the regulation of turnover metabolism of muscle protein alone.

Rennie et al. (1986) thought that the synthesis and degradation of muscle protein were controlled by the size of glutamate / glutamine pool. Many experiments in vivo and in vitro confirmed that there was a linear relationship between the concentration of glutamate / glutamine in muscle and the rate of egg synthesis (Rennie et al., 1986; mcnurlan et al., 1987);

Jepson et al., 1988). Glutamate / glutamine transport out of muscle cells is mainly regulated by Na + carrier. Increasing the concentration of Na + in cells, such as injury, long-term disease and septicemia, will lead to the rapid loss of glutamate / glutamine and accelerate the degradation of muscle protein. Leucine interferes with the hydrolysis of muscle protein, which may also be due to its noncompetitive inhibition of glutamate / glutamine Results of amine efflux (Rennie et al., 1986).

However, when glutamic acid is supplied to surgical patients in the form of peptide, it can partially reduce the negative nitrogen balance and prevent the loss of muscle AA, while the free form is not (Stehle research, 1989); darmaun et al. (1994) observed that whether glutamine peptide is supplied from the gut or parenteral, it can improve the protein synthesis and leucine balance of the body.

SP and FAA play different roles in AA utilization and protein metabolism of intestinal tissue.

Many experiments on rats with short-term starvation or long-term low energy and low protein nutrition showed that different molecular forms of AA had different effects on the membrane morphology, brush border membrane and peptidase activity (poullain et al., 19891991; infante et al., 1992; botsios et al., 1993).

In addition to protein depletion, the direct utilization of nutrients by intestinal cells is usually limited. Hirschfield et al. (1963) and Alpers (1972) observed that the distribution pattern of protein in vivo was completely different between oral AA and intravenous AA. The vast majority of AA injected intravenously was labeled in the protein of the cells at the junction of the gland fossa and microvilli and the gland fossa, while the vast majority of AA injected through the intestinal cavity was labeled in the cell protein at the top of the villus of the intestinal mucosa.

Johnson (1988) thought that the mature undifferentiated intestinal cells at the top of villi mainly absorbed AA injected from the intestinal cavity, while the AA of the adenoid cells responsible for cell growth came from the blood. Therefore, only the AA absorbed into the circulation and transported to the intestinal tissue can participate in the synthesis of intestinal tissue proteins. Le Guowei (1996) found that the protein synthesis rate of intestinal tissue in group SP was higher than that in group FAA.

Hagiwara et al. (1995) showed that lactoferrin and its pepsin hydrolyzed peptide can promote the proliferation of intestinal epithelial cells, in addition, lactoferrin can also promote the growth of cells, and promote thymine incorporation into the DNA of rat adenopit cells;

When weaned piglets were fed three types of diets (whole plant protein diet, compound balanced AA diet and compound protein diet), the morphological structure of intestinal mucosa and the morphological structure of colonic epithelial cells were significantly different (Dong Guozhong et al., 1994).

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Chengdu Shengnuo Biotechnology Co., Ltd. has "Chengdu polypeptide drug engineering technology research center" in Chengdu, mainly engaged in polypeptide, polypeptide drug and beauty peptide research. Our zero defect has passed the FDA certification, and now it has become the first-class professional peptide drug and product development, technology transfer, technical service and peptide drug industry in the scale production and export of China's parks.