Hydroxylysine: isolation from gelatin and resolution of its diastereoisomers by ion exchange chromatography.

Since the isolation of hydroxylysine as the picrate from the phosphotungstic acid-precipit>able fraction of gelatin acid hydrolysates by Van Slyke, Hiller, Dillon, and MacFadyen (I), other isolation procedures have been reported (2, 3). The most, recent is t.hat of Sheehan and Bolhofer (4) who used chromatographic: techniques in part to obtain analytically pure hydroxylysine from gelatin.’ The present paper describes a chromatographic procedlue whereby, without preliminary removal of cystine or arginine, all of the hydroxylysine in a hydrochloric acid hydrolysate of 100 gm. of gelatin was separated from the other amino acids. Separation was partially effected on a column of Amberlite In-1 20 and was completed on a column of Dowex 50. From the effluent of the Dowex column, hydroxylysine monohydrochloride of 98 per cent purity was isolated in yields of 80 to 90 pcl cent. A single crystallization from aqueous alcohol gave analytically pure but partially racemized hydroxylysine in yields of 70 to 85 per cent of the original material. The hydroxylysine from gelatin was resolved by chromatography into hydroxylysine and allohydroxylysine, a result in accord with Piez (6) who separated a synthetic mixture of hydroxy-n-lysine from allohydroxy-nlysine similarly. Piez also made the observation that approximately 20 per cent of the hydroxylysine in acid hydrolysates of tooth collagen was allohydroxylysine. The present study indicates that allohydroxylysine is an