Abstract
It has recently been shown that, in addition to free hydroxyproline and dialyzable hydroxyproline-peptides, there is also present in human plasma a form of hydroxyproline which is non dialyzable, precipitable with protein precipitants.
The purpose of this work is to clarify the biological and clinical significance and character of the hydroxyproline-containing protein in plasma.
The following results were obtained in this work.
1) Elevation of plasma protein-bound hydroxyproline in hyperthyroidism and chronic hepatitis was confirmed.
2) Plasma protein-bound hydroxyproline of rat elevated after treatment with L-thyroxine or β-aminopropionitrile.
3) Two fractions were obtained by gel filtration with Sephadex G-100 of non dialyzable portion of hot TCA extract from cold TCA precipitate. The first fraction contained little hydroxyproline, and the second one contained much hydroxyproline.
4) Hydroxyproline was mostly collected in 0.05-0.1M NaCl eluted fraction by DEAEcellulose column chromatography of the second fraction in gel filtration.
5) It was indicated by the use of DNP method and paper chromatography of DNP-peptides that the hydrolysate with collagenase of 0.05M NaCl eluted fraction included a tripeptide, glycylprolyl-hydroxyproline. It has been known that this tripeptide is in the specific amino acidsequences of collagen.
6) A hydroxyproline-containing protein was isolated to disc electrophoretically single band by means of extraction with acetic acid, isoelectric precipitation, DEAE-Sephadex chromatography and disc electrophoresis. This protein migrated in disc electrophoresis as plasma proteindid.
From these results, it is most likely that plasma hydroxyproline-containing protein is plasma proteins which bind fragments of collagen.
