Role of Digestive Enzymes in the Permeability of the Enterocyte

Ugolev, A. M.; Iezuitova, N N; Smirnova, L F

doi:10.1007/978-3-642-69508-7_2

Cited by 3 publications

(2 citation statements)

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“…Bağırsak Absorbsiyonları: Bağırsağın ana fonksiyonu bilindiği gibi yiyeceklerin ve özellikle de proteinin sindirilmesi ve absorbsiyonudur (11). Burada peptit, parçalayıcı enzimlerle karşı karşıya gelir (12). Bağırsak lümeni içinde, pankreatik endopeptidazlar (özellikle de tripsin, elastas ve kimotripsin), eksopeptidazlar (karboksipeptidaz A ve B) yardımıyla amino asitler ve 2-6 amino asit uzunluğunda peptitler üretilmektedir.…”

Section: Metaboli̇zma Ve İtrahunclassified

Peptit yapılı ilaçların rasyonel tasarımına yönelik yeni gelişmeler: recent advances towards the rational design of peptide drugs

Yeşilada¹

2004

Ankara Universitesi Eczacilik Fakultesi Dergisi

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ÖZET ABSTRACTIn this review, after a short introduction to definition and physiological roles of regulatory peptides, problems faced during the development of peptide drugs, studies directed to solve these problems and rational design of peptide drugs with special emphesis on peptidomimetics are mentioned.Key Words: Peptides, endojen peptides, peptidomimetics, back-bone modifications GİRİŞGeçtiğimiz on-onbeş yıl içinde, hastalıkların teşhisi ve tedavisinde önemli gelişmeler olmuştur. Endojen peptitlerin ve proteinlerin hayati olayların düzenlenmesinde oynadıkları rolün öneminin anlaşılması bu gelişmelere ivme kazandıran önemli bir aşamadır. Doğal peptitlerin ilaç olarak kullanılması 1960'lı yılların başlarına kadar uzanmaktadır. Oksitosin, lis-vasopressin, kortikotropin, pentagastrin gibi hormonların sentezi ve piyasaya sürülmesi ile yaşanan bu dönemi , yetmişli yıllarda bir çok laboratuarın kapanmasına neden olan durgun bir dönem takip etmiştir.Bunun nedenleri doğal peptitlerin dayanıksız olmaları nedeniyle etki sürelerinin kısa olması,

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Section: Metaboli̇zma Ve İtrahunclassified

Peptit yapılı ilaçların rasyonel tasarımına yönelik yeni gelişmeler: recent advances towards the rational design of peptide drugs

Yeşilada¹

2004

Ankara Universitesi Eczacilik Fakultesi Dergisi

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“…The process whereby an oligomeric nutrient is hydrolyzed immediately outside of the cell prior to its uptake is well known and is often referred to as “membrane digestion” (Ugolev 1965). It is much studied for the utilization of oligoand polysaccharides by metazoan enterocytes (Ugolev et al 1984; Semenza 1987) and cestode tegument.…”

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Purification and Specificity of Two α‐Glucosidase Isoforms of the ParasiticProtist Trichomonas vaginalis

Kuile

Sánchez

Müller

2000

J Eukaryotic Microbiology

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Two isoforms of alpha-glucosidase were purified from the parasitic protist Trichomonas vaginalis. Both consisted of 103 kDa subunits, but differed in pH optimum and substrate specificity. Isoform 1 had a pH optimum around 4.5 and negligible activity on glucose oligomers other than maltose, while isoform 2 with a pH optimum of 5.5 hydrolyzed also such substrates at considerable rates. Neither had activity on glycogen or starch. Isoform 1 had a specific activity for hydrolysis of maltose of 30 U/mg protein and isoform 2 101 U/mg protein. The Km values were 0.4 mM and 2.0 mM, respectively. Isoform 2 probably corresponds to the activity detected on the cell surface.

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Maltose utilization by extracellular hydrolysis followed by glucose transport in Trichomonas vaginalis

Kuile

Müller

1995

Parasitology

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The amitochondriate parasitic protist Trichomonas vaginalis can utilize either glucose or maltose as carbon and energy source. The mechanisms of maltose utilization were explored with uptake experiments using radio-isotope labelled maltose in combination with the silicone-oil centrifugation technique and enzymatic assays measuring maltose hydrolysis. The uptake of maltose label became saturated after 2-3 h. The uptake of maltose as a function of the external maltose concentration was linear at low concentrations with no further increase at higher levels, kinetics characteristic of reactions obeying Michaelis-Menten kinetics preceded by a diffusion-limited step. Increased viscosity of the medium resulted in decreased maltose uptake, indicating an extracellular location of the diffusion-limited step. Most of the cellular alpha-glucosidase activity of T. vaginalis was detected on the cell surface, suggesting that maltose is hydrolysed to glucose outside the cell. Glucose interfered more with maltose uptake, and maltose less with glucose uptake, than would be expected if 1 mol of maltose were the equivalent of 2 mol of glucose. This pattern of interaction indicated that the interference occurs before the common metabolic pathway and even before the transport step, supporting the idea of extracellular maltose hydrolysis. We conclude that maltose is hydrolysed to glucose in the boundary layer of the cell, a process akin to membrane digestion in vertebrate enterocytes and on the teguments of helminths. The glucose formed is then transported by the glucose carrier of the organism.

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Role of Digestive Enzymes in the Permeability of the Enterocyte

Cited by 3 publications

References 273 publications

Peptit yapılı ilaçların rasyonel tasarımına yönelik yeni gelişmeler: recent advances towards the rational design of peptide drugs

Peptit yapılı ilaçların rasyonel tasarımına yönelik yeni gelişmeler: recent advances towards the rational design of peptide drugs

Purification and Specificity of Two α‐Glucosidase Isoforms of the ParasiticProtist Trichomonas vaginalis

Maltose utilization by extracellular hydrolysis followed by glucose transport in Trichomonas vaginalis

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