Hydroxyproline in collagen

Modified amino acids, which occur in special proteins such as hydroxyproline in collagen and 3-methylhistidine in actin and myosin, can be used as indicators of the degradation of these proteins. 

Perret, S., Merle, C., Bernocco, S., Berland, P., Garrone, R., Hulmes, D.J., Theisen, M., and Ruggiero, F. (2001). Unhydroxylated triple helical collagen I produced in transgenic plants provides new clues on the role of hydroxyproline in collagen folding and fibril formation. J. Biol. Chem. 276, 43693-43698. 

Ahnoff, M., Grundevik, I., Arfwidsson, A., Fonselius, J., and Persson, B.-A., Derivatization with 4-chloro-7-nitrobenzofurazan for liquid chromatographic determination of hydroxyproline in collagen... 

Table I. Mole Ratio of Proline to Hydroxyproline in Collagen Isolated from Granuloma of Normal and Scorbutic Guinea Pigs0...

The answer is e. (Murray, pp 627-661. Sciiver, pp 3897-3964. Sack, pp 121-138. Wilson, pp 287-320.) Ascorbic acid (vitamin C) is found in fresh fruits and vegetables. Deficiency of ascorbic acid produces scurvy, the sailor s disease. Ascorbic acid is necessary for the hydroxylation of proline to hydroxyproline in collagen, a process required in the formation and maintenance of connective tissue. The failure of mesenchymal cells to form collagen causes the skeletal, dental, and connective tissue deterioration seen in scurvy. Thiamine, niacin, cobalamin, and pantothenic acid can all be obtained from fish or meat products. The nomenclature of vitamins began by classifying fat-soluble vitamins as A (followed by subsequent letters of the alphabet such as D, E, and K) and water-soluble vitamins as B. Components of the B vitamin fraction were then given subscripts, e.g., thiamine (Bi), riboflavin (B2), niacin [nicotinic acid (B3)], panthothenic acid (B5), pyridoxine (Bg), and cobalamin (B ). The water-soluble vitamins C, biotin, and folic acid do not follow the B nomenclature. 

Table 9.16 shows the incorporation of [ H proline into hydroxyproline in collagen formed by granuloma tissue from control and vitamin C-defIcient (scorbutic) guinea pigs, and Table 9.17 the effects of various inhibitors of transcription and translation on the stimulation by ascorbate of proline hydroxylation in mouse fibroblasts in culture. 

Table 9.16 Incorporation of radioactivity from fHpproline into hydroxyproline in collagen granuloma tissue from control and vitamin C-deficient (scorbutic) guinea pigs...

The biogenesis of the hydroxyproline in collagen has long been under investigation yet the mechanism of its formation and incorporation into protein is still not fully understood. As L-proline- N but not hydroxyproline- N serves as the precursor of the hydroxyproline in collagen (Stetten and Schoenheimer, 1944 Stetten, 1949) it has been postulated that the imino acid may be formed from peptide-bound proline or be derived from an activated rather than a free form of proline. Studies with C-labeled proline and hydroxyproline have confirmed... 

While there is evidence that some modification reactions take place while the growing polypeptide chain is still attached to the polysomes, most modifications occur after release of the chain from the ribosome. Examples of processing of chains still on the ribosome include formation of hydroxy lysine and hydroxyproline in collagen elaboration. 

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