Question

Hirudin is
(a) A lysine-rich protein produced by Hordeum vulgare.
(b) A toxic molecule isolated from Gossypium hirsutum which reduces human fertility.
(c) An anticoagulant protein that can be obtained from transgenic Brassica napus.
(d) An antibiotic produced by a genetically engineered Escherichia coli.

Answer 1

Hint: Hirudin is a protein found mainly in the salivary glands of leeches and it has an important role in their alimentary habit. Generally, it is considered to be an inhibitor of the enzyme thrombin.

Complete answer:
Hirudin is the protein that is obtained from transgenic Brassica napus and acts as an anticoagulant i.e. it prevents blood from clotting. The genes of hirudin protein were chemically synthesized and were transferred into the Brassica napus where it accumulated in the seeds. Then it is extracted and purified.
So, the correct answer is ‘An anticoagulant protein that can be obtained from transgenic Brassica napus’.

Additional Information: Hirudin, the coagulant peptide, is found in the salivary glands of blood-sucking leeches. This protein is essential for the alimentary process of leeches.
It is made of 65 amino acids, organized into a compact N-terminal domain-containing three disulfide bonds and one C-terminal domain.
We all know that at the final stage of blood coagulation, fibrinogen turns into fibrin by the enzyme named thrombin. The main inhibitor of thrombin in blood circulation is called antithrombin. Hirudin is similar to antithrombin and acts as an inhibitor of thrombin. But unlike antithrombin, it binds to and inhibits only the thrombin that is activated. Thus it prevents the formation of clots. It has therapeutic value in diseases like blood coagulation disorders, skin hematomas, varicose veins, etc.
Keeping an eye on the difficulty of extracting large amounts of hirudin from natural sources, recombinant biotechnology is being used to produce and purify these proteins. This helped us to develop hirudin based anticoagulant products.

Note: In order to produce hirudin protein, a plant oleosin was used as a carrier. These oleosin-hirudin fusion proteins were expressed and accumulated in seeds. The protein was targeted to the oil body membrane and separated from the majority of other seed proteins by floating centrifugation and hirudin was localized to the surface of oil bodies. This oleosin fusion protein system helped in the large scale production of hirudin protein as it is very difficult to produce normally from natural sources.