[The final stages in the hydrolysis of foodstuffs in the small intestine of mammals with different food specializations]. / Zakliuchitel'nye étapy gidroliza nekotorykh pishchevykh veshchestv v tonkoi kishke mlekopitaiushchikh s raznoi pishchevoi spetsializatsiei.

The activity of the small intestine's enzymes realising final stages of nutrients hydrolysis was studied in herbivorous, omnivorous and carnivorous animals. The small intestine's enzyme spectrum corresponded to the food specialisation of the animals. The proximal-distal gradient of the distribution of digestive enzymes along the small intestine has both some similar features and certain differences.

[Induced autolysis as an important mechanism of the initial stages of ordinary digestion]. / Indutsirovannyi autoliz kak vazhnyi mekhanizm nachal'nykh stadii pishchevareniia v estestvennykh usloviiakh.

The critical review of generally accepted ideas on initial stages of digestion in higher animals is presented. A brief account is given of the hypothesis of the induced autolysis as an important mechanism of food assimilation. According to this hypothesis digestive juices (in addition to their enzyme activities) contain factors capable to induce the autolysis of food structures. An attempt was made to estimate the value of gastric secretions and induced autolysis in the splitting of complex biological food structures. The splitting of native structures of food object was found to be more effective and complete than the splitting of the same structures subjected to heat denaturation. The results obtained suggest that the initial stages of digestion should be considered as a complex process provided both with the enzymes of gastric juice and with the enzymes of food itself, with lysosomal enzymes in particular.

[Enzymatic adaptation of the pancreas and small intestine to food composition (the example of carbohydrases)]. / Fermentnye adaptatsii podzheludochnoi zhelezy i tonkoi kishki k kompozitsii pishchi (na primere karbogidraz).

In two series of experiments on rats, the effect of high protein as well as fat and carbohydrate diets of carbohydrases activity of the pancreas and the small intestine was studied; in the first series, the animals had the specialized diets for 4, 15 and 30 days, while in the second series--for 7 days. In the 1st series food composition produced an obvious effect on gamma--amylase, maltase and sacrase activities of the intestinal mucosa, whereas in the 2nd series the effect was insignificant which can be accounted for by somewhat different conditions of the experiments. The data suggest that adaptation of pancreatic and small intestine's enzyme systems to food composition should be considered an integrated reaction.

[Radial and proximo-distal distribution of hydrolytic enzymes in the small intestine at rest and during digestion]. / Radial'noe i proksimo-distal'noe raspredelenie gidroliticheskikh fermentov v tonkoi kishke v pokoe i pri pishchevarenii.

Alpha-amylase was present in considerable amount in the chyme in rats both at rest and during digestion, in the latter case its level being increased. Activity of intrinsic intestinal enzymes dominated in the homogenate of the mucosa. Transition from fasting to feeding and digestion increased the level of alkaline phosphatase and dipeptidase activities in the homogenate of the mucosa. The data obtained suggest the final stages of biopolymers' hydrolysis to be localized in various enterocyte structures. The surface mucus, owing to absorbed pancreatic enzymes, binding proteins and other types of physiologically active molecules, is assumed to play the role of a specific molecular filter and take part in the initial stages of digestion.

[The hydrolases of the mucosal, submucosal and muscular layers of the small intestine and their functions]. / Gidrolazy mukoznogo, submukoznogo i myshechnogo sloev tonkoi kishki i ikh funktsii.

Proceeding from the newly obtained evidence on the distribution of digestive enzymes in mucosal, submucosal and muscular layers of the small intestine in rats, a hypothesis has been formulated: in addition to the enterocyte enzyme complex forming the epithelial barrier, there seems to exist a postepithelial barrier formed by the enzymes localized in subepithelial structures. The efficiency of this second barrier was manifested by the study of the peptide hydrolysis and transport using everted intact and de-epithelialized intestinal sacs.

[Proteases of the large intestine]. / Proteazy tolstoi kishki.

The large intestine was found to reveal an obvious activity of various aminopeptidases and genuine dipeptidases in dogs and in humans. A dipeptidase was found specific by its independence of the C-terminal configuration of the peptide. This peptidase in an intrinsic membrane protein. Physiological significance of these enzymes is discussed.

[The circadian rhythms of the hydrolytic enzyme activity of the small intestine in fasting and satiated rats]. / Tsirkadnye ritmy aktivnosti gidroliticheskikh fermentov tonkoi kishki golodnykh i sytykh krys.

The maximal activity of membrane enzymes (carbohydrases, alkaline phosphatase, aminopeptidase) was demonstrated in the evening, but that of cytosolic dipeptidases--at night and at day. This is possibly connected with the different functions of the enzymes--digestive or catabolic, resp. The circadian rhythm did not depend on functional states. The circadian rhythms of the enzymes activities were more expressed in the epithelial layer of the small intestine than in the subepithelial (stromal and muscle-serosal) ones.

[Hydrolases in the large intestine in rats with various experimental pathologies]. / Gidrolazy tolstoi kishki pri razlicnhykh formakh éksperimental'noi patologii u krys.

In the colon mucous membrane, activity of a wide range of membrane and mainly intracellular enzymes was studied in the organism at different conditions. The data obtained suggest participation of digestive hydrolases in the colon not only on postdigestive processes but, in certain states of the organism, in digestive processes too.

Substrate interactions on the intestinal mucosa: a concept for the regulation of intestinal digestion.

1. The hydrolysis of glycyl-L-leucine, glycyl-L-tyrosine, tributyrin, sucrose, maltose, soluble starch and alpha- and beta-glycerophosphates by everted segments of rat intestine was estimated separately or in combination. 2. A comparative study showed significant interaction between different substrates which affected their digestion. 3. Two types of interaction were identified: products of hydrolysis (1) affected the hydrolysis of homologous substances, e.g. methionine and alanine inhibited glycyl-L-leucine hydrolysis, maltose reduced glucoamylase (alpha-1,4-glucan glucohydrolase; EC 3-2-1-3) activity (intracatenary interactions); (2) interfered with the hydrolysis of a different group of substances, e.g. tributyrin inhibited dipeptidase (glycyl-L-leucine hydrolase; EC 3-4-3-2) and alkaline phosphatase (EC 3-1-3-1), glycyl-L-leucine interfered with the activity of the latter enzyme (intercatenary interactions). 4. Mechanisms of interactions were suggested by the results of a comparison of the extent of inhibition or activation of two enzymes (glycyl-L-leucine hydrolase and alkaline phosphatase) in situ in everted intestinal segments or after solubilization with papain or Triton X-100, and different treatments known to affect allosteric sites of these enzymes. 5. Tributyrin and dipeptides were found to act on alkaline phosphatase as allosteric regulators. A discontinuity of the Arrhenius plot suggested the existence of different enzyme conformations which were re-arranged by tributyrin. 6. Substrate interactions in digestion were found in adult rat, cat, rabbit and hen. Substantial differences were found between classes (Aves and Mammalia), orders (rodents, lagomorphs and carnivores) and between age-groups within an animal strain (in this instance, for the rat). 7. These interactions are thought to be involved in the co-ordination of digestion with intestinal absorption and to regulate the time and site of subsequent hydrolysis.

Membrane and intracellular hydrolysis of peptides: differentiation, role and interrelations with transport.

The possible relative importance of the membrane and intracellular peptidases of the enterocytes in splitting dietary peptides to amino acids has been analysed. On the anoxic criterion, membrane hydrolysis was found to be predominant. Model experiments revealed cooperative interactions between the membrane enzyme and the coupled transport system. This cooperativity allows the main characteristics of oligomer transport to be described in terms of membrane digestion. Comparison of the behaviour of membrane and intracellular peptidase under different conditions has shown that the former are largely involved in digestion and the latter in intracellular metabolism. It is suggested that the efficiency of the membrane system is high enough to account for the hydrolysis of protein, especially taking into account the stimulation of enzyme processes in the brush border that occurs after ingestion of protein and carbohydrate. A sequential model based on the concept of three interacting enzyme layers (glycocalyx, lipoprotein membrane and cytosol) is presented.