Question

Нужна помощь по биохимии Яд некоторых змей содержит фермент фосфолипазу А-2. Если к цельной крови добавить небольшое количество яда, то быстро наступает гемолиз эритроцитов. Напишите реакцию, которая будет происходить под действием фермента фосфолипазу А-2 - компонента яда при взаимодействии с фосфолипидами крови. Объясните, почему при добавлении змеиного яда к крови происходит гемолиз эритроцитов.

Answer 1

Ответ:

R1-C(O)-O-CH2-CH(O-C(O)-R2)-CH2-O-PO3-X (фосфолипид - компонент клеточной мембраны) + фосфолипаза А-2 (гидролизует связь O-C(O)- у 2 атома C остатка глицерина) + H2O = R1-C(O)-O-CH2-CH(OH)-CH2-O-PO3-X (2-лизофосфолипид) + R2-COOH (жирная к-та);

гидролиз фосфолипида, как компонента клеточной мембраны, приводит к снижению эластичности и появлению в ней "дыр", через которые вода проникает внутрь эритроцита, что способствует его набуханию, а затем и разрушению с выходом гемоглобина (гемолизу).

Answer 2

Reaction catalyzed by phospholipase A-2

Phospholipase A-2 (PLA-2) is an enzyme that catalyzes the hydrolysis of phospholipids, specifically the cleavage of the ester bond between the fatty acid at the sn-2 position and the glycerol backbone of phospholipids. The reaction can be represented as follows:

Phospholipid + H2O → Lysophospholipid + Free fatty acid

The specific reaction catalyzed by phospholipase A-2 depends on the type of phospholipid present in the blood. Different phospholipids have different fatty acids attached to the sn-2 position, and the cleavage of the ester bond by PLA-2 results in the release of specific lysophospholipids and free fatty acids.

Hemolysis of erythrocytes under the action of phospholipase A-2

When a small amount of snake venom containing phospholipase A-2 is added to whole blood, it can rapidly induce hemolysis of erythrocytes. This occurs due to the interaction between the enzyme and the phospholipids present in the blood.

Phospholipids are an essential component of cell membranes, including the membranes of erythrocytes. The hydrolysis of phospholipids by phospholipase A-2 leads to the formation of lysophospholipids and free fatty acids. The lysophospholipids disrupt the integrity of the erythrocyte membrane, causing it to become leaky and leading to the release of hemoglobin into the surrounding medium. This process is known as hemolysis.

The released hemoglobin can then bind to other molecules, such as oxygen, and form complexes that can be toxic to the body. Additionally, the disruption of erythrocyte membranes can impair their ability to transport oxygen and carbon dioxide, leading to further complications.

In summary, the reaction catalyzed by phospholipase A-2 in the presence of snake venom leads to the hydrolysis of phospholipids in the blood, resulting in the formation of lysophospholipids and free fatty acids. This, in turn, causes the disruption of erythrocyte membranes and the subsequent hemolysis of erythrocytes.

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