Table 5. Glycosidases

Enzyme	Reaction	Localization
Alfa-amylase	Starch, glycogenàmaltose	Cells, saliva, pancreatic juice
Gamma-amylase	Glycogenàglucose	Liver
Maltase	Maltoseà2 glucose	Cells, intestinal juice
Lactase	Lactoseàglucose + galactose	Cells of mamma, intestinal juice
Sucrase	Sucroseàglucose + fructose	Intestinal juice
Cellulase	Cellulose	Intestinal juice of cow, horse

So, carbohydrases aren’t in gastric juice.

3. Esterases is next subclass and it is subdivided into the 2 sub-subclasses – lipases and phosphoesterases. 1. lipases act on triglycerides or neutral fats to liberate glycerol, fatty acids and mono- and diglycerides. 1) Lipase of gastric juice is active at pH 3-5 only. The pH of gastric juice of adult people is 1.5-2.0, therefore this enzyme is active in gastric of baby (child arms) when pH of gastric juice is 3-5. This enzyme acts on emulgated fat of milk only. 2) lipase of pancreatic juice is secreted by pancreatic cells in inactive form, one is activated by conjugated salts of bile acids. After activation lipase of pancreatic juice is very important enzyme in the digestion of fat. It acts on the triglycerides and splits them to fatty acids and monoglycerides.

3) intestinal lipase is secreted by mucous cells of intestine in active form and acts on the monoglycerides:

So, under the action of lipases in gastrointestinal tract triglycerides split to glycerol, fatty acids and monoglycerides. 4) cholesterase hydrolyzes cholesterol esters. 5) phospholipases A1, A2 hydrolyzes the ester bond at 1-st and 2-nd position in phospholipids. 2. Phosphoesterases hydrolyze the phosphoester bond. 1) phospholipases C and D hydrolyze the splitting the bond between glycerol and phosphoric acid (phospholipase C) and between phosphoric acid and nitro-containing matters (phospholipase D). 2) phosphatases – ATP-ase and glucoso-6-phosphatase.

Other hydrolases:

1. deaminases or aminohydrolases. These include adenase and guanase, which catalyze the following reactions: adenine + H2O à hypoxanthine + NH3; guanine + H2O à xanthine + NH3; hypoxanthine à xanthine à ureatic acid.

2. Deamidases or amidohydrolases catalyze the hydrolysis of amides and include urease, arginase, glutaminase and asparaginase, which catalyze the following reactions respectively: urea + H2O à CO2 + 2 NH3; arginine + H2O à ornithine + urea; Gln + H2O à Glu + NH3; Asn + H2O à Asp + NH3

3. phosphatases - a greit variety of phosphotases is found. These occur in many tissues: acid and alkaline phosphotases, phosphodiesterase, phosphorylase, pyrophosphatase.

4. Nucleases (polynucleotidases). These are present in the intestinal juice and tissues. These decompose nucleic acids (DNA and RNA) to mononucleotides. DNA and RNA à n (mononucleotides).

5. Nucleotidases – these enzymes occur in the intestinal juice and tissues and hydroluze mononucleotides and H3PO4.

6. Nucleosidases these catalyze the following types of reactions: nucleoside + H3PO4 à free nitrogenous bases ( purine or pyrimidine) + sugar phosphate.

The use of hydrolases

1. enzyme substitution in digestive disturbances. The enzyme preparation used for the digestive disturbances contain proteinases, lipases and amylases of animal, vegetable and microbial origin. Pepsin and pancreatin (containing all enzymes of pancreatic juice) alone or along with dry bill powder are the most frequently used enzyme preparation in digestive disorders: for example, kreon, festal ect.

2. Blood coagulation. Trombin in used locally to stop bleeding urokinase and streptokinase are used to produce lysis of blood clots (tromboflebits, infaretus).

3. For lysis different hematomas, plastic surgery, trauma of face, box.

4. To increase blood supply to tissues. The enzyme kallicrein increases the formation of kinins from their precursors – kininogens, kinins produce vasodilatation and for this reason kallicrein is used in cases of impairment of the blood supply of tissues of the extremity and heart.

5. Locally applied enzyme preparations – 1) hyaluronidase – this enzyme hydrolyzes mucopolysaccharides, such as hyaluronic acid and chondroitin sulfatic and thus causes a loosing of the deep layers of the skin. It has been used for increasing the rate of fluid absorption from subcutaneous tissues and in the treatment of sprains, hematomas and thrombophlebitis.

6. Trypsin and chymotrypsin. These are used to degrade necrotic tissue, masses of pus, secretions and effusions thus producing a cleaning of the wounds and accelerating wound healing. Chymotrypsin is also used orally and by injection in these conditions (pneumonia, abscess, pleurit, pyelonephrite).

7. RNA-ase and DNA-ase. These are used in the form of streptodornase for the disintegration of pus.

8. Enzymes for cancer treatment. L-asparaginase has proved very useful in the therapy of limphoblastic leukemia especially in children. L-asparagine is substrate of this enzyme, is essential for the proliferation of cancer cells. Administration of L-asparaginase hydrolyzes asparagine and results in a decreased availability of asparagine to cancer cells and therefore their abnormally fast growth is arrested resulting in a remission.

9. Treatment of old age.

10. For treatment of renal deficiency is used urease

The use of hydrolases in industry

1. catepsins for treatment of meat.

2. In cheese dairy making.

3. In washing powder (proteases, lipases).

<== попередня сторінка	\|	наступна сторінка ==>
III. Hydrolases	\|	The general characteristic of transferases

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