Hydroxyproline

Overview

Chemical structure of Hydroxyproline

Hydroxyproline is a non-essential amino acid that plays a critical role in the stability of the collagen triple helix. It is derived from the amino acid proline and is a major component of the protein collagen, which is found in connective tissues such as skin, tendons, and bones.

Structure and Properties

Hydroxyproline is unique among amino acids due to the presence of a hydroxyl group attached to the pyrrolidine ring of proline. This modification is catalyzed by the enzyme prolyl hydroxylase, which requires vitamin C as a cofactor. The hydroxylation of proline residues in collagen is crucial for the formation of stable collagen fibers.

Biosynthesis

The biosynthesis of hydroxyproline occurs post-translationally, meaning it is synthesized after the protein chain has been formed. The enzyme prolyl hydroxylase hydroxylates proline residues in the collagen polypeptide chain, converting them into hydroxyproline. This process is essential for the proper folding and stability of collagen.

Function

Hydroxyproline contributes to the stability of collagen by forming hydrogen bonds between the collagen chains. This stabilizing effect is critical for maintaining the structural integrity of connective tissues. The presence of hydroxyproline is also used as a marker for collagen content in biological samples.

Clinical Significance

Deficiencies in vitamin C can lead to impaired hydroxylation of proline, resulting in weakened collagen fibers and the clinical condition known as scurvy. Symptoms of scurvy include bleeding gums, joint pain, and poor wound healing, all of which are related to defective collagen synthesis.

Applications

Hydroxyproline is used in various biochemical assays to measure collagen content in tissues. It is also studied in the context of fibrosis, where excessive collagen deposition occurs, and in the development of collagen-based biomaterials for medical applications.

Related pages

• Collagen
• Proline
• Vitamin C
• Scurvy
• Amino acid