Connective Tissue Fibrous Proteins

Question 1

What are the stages of formation of collagen?

Answer 1

A. Synthesis of procollagen which is secreted from the cell

B. Cleavage to tropocollagen by procollagen peptidase

C. Assembly of tropocollagen leading to the formation of collagen fiber

D. Crosslinking of tropocollagen to strengthen the fiber

Question 2

What is the name of the disease that arises from an inability to secrete procollagen? Describe this disease.

Answer 2

Osteogenesis imperfecta. The genetic defect leading to this disease is due to a mutation in the collagen gene: a buried Glycine residue is mutated to Cystein.

Question 3

What is the name of the disease resulting from a problem in the second step of collagen formation? Describe this disease.

Answer 3

Ehlers-Danlos syndrome. This disease results from reduced levels of procollagen peptidase, so procollagen is not fully converted into tropocollagen. This prevent lysyl oxidase from acting on tropocollagen to create the crosslinks.

Question 4

What does Lysyl oxidase do?

Answer 4

Converts lysine to allysine.

Question 5

What is the name of the disease resulting from a problem in the third step of collagen formation? Describe this disease.

Answer 5

Scurvy. This is due to a deficiency in the enzyme that forms hydroxyproline (prolyl hydroxylase). The OH group of hydroxyproline is essential for the hydrogen bonds needed to form collagen fibers.

Question 6

What is the name of the disease resulting from a problem in the fourth step of collagen formation? Describe this disease.

Answer 6

Lathyrism. Deficiency of lysyl oxidase enzyme. Lack of cross link formation
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