Proteins of the periodontium. Biochemical studies on the collagen and noncollagenous proteins of human gingivae

. Insoluble collagen was prepared from gingivae of full term, stillborn infants (SI) and from that of patients exhibiting gingival hyperplasia that was secondary to diphenylhydantoin therapy (DPH). During the preparations only 4 % of the collagen from DPH was extracted and 17 % from SI gingivae was solubilized, by neutral salt and dilute acid extractants. Subsequent amino acid analysis indicated the presence of a relatively large quantity of the noncollagenous protein(s) in the DPH collagen preparation. After collagen samples were converted to soluble cyanogen bromide (CNBr) pep‐tides, the noncollagenous protein(s) proved to be insoluble in the dilute citrate buffer routinely used for initial chromotographic separation of the CNBr peptides. This fraction, whether from DPH or SI gingivae, had essentially the same composition. The noncollagenous protein fraction comprised about 7 and 20 %, respectively, of the dry weights of the SI and DPH insoluble collagen preparations. CNBr peptides from gingival collagen have been purified and shown to be identical with those reported for human skin collagen. Thus, the collagen of gingivae is principally of the type with the chain structure [αl(I)]2α2. Preliminary data strongly suggest the presence in gingivae of a lower level of collagen of the [al (III)]s type.