The Amino Acid Composition of Enamel Protein

Abstract

B Y THE use of paper chromatography, Block, Horwitt, and Bolling' showed qualitatively that human enamel eukeratin contained most of the known amino acids, and gave quantitative values for arginine, histidine, and lysine.Losee and Hess,2 who had prepared the protein analyzed by Block, Horwitt, and Bolling, determined cystine, methionine, and phenylalanine by colorimetric methods and subsequently3 also determined arginine, histidine, and lysine, and confirmed the statement that the normal enamel protein is an eukeratin. However, the sum of the values for these six amino acids accounts for less than 15 per cent of the total nitrogen of the protein. In order to characterize completely the protein and also to permit comparison with dentinal protein and other eukeratins, we have estimated the other amino acids in normal enamel protein. EXPERIMENTALThe enamel protein was prepared as described by Losee and Hess.2 The nitrogen content was 13.59 per cent and the ash content was 9.59 per cent, based upon the weight of the desiccator-dried sample. The amino acids, except the six previously determined colorimetrically, were all estimated by the microbiologic methods used by Horn, Jones, and Blum.4 The inoculumns were prepared using the media of Hac, Snell, and Williams5 because the liver infusion used by Horn, Jones, and Blum4 was unavailable. Leuconostoc mesenteroides was employed for the assay of leucine and isoleucine, and Streptococcus faecalis for threonine and valine as recommended by Horn, Jones, and Blum.4 Leucine, isoleucine, valine, glutamic acid, aspartic acid, proline, glycine, and tyrosine were determined, as suggested by Neuman,6 using Leuconostoc mesenteroides and serine employing Streptococcus faecalis. For each amino acid from three to four concentration ranges and triplicate determinations for each concentration were made, of the resulting lactic acid using 0.05 N NaOH and bromthymol blue as the indicator. The results were averaged.The protein was hydrolyzed with 20 per cent hydrochloric acid for six hours at 125°C., and the hydrolysate was freed from excess acid by evaporation under reduced pressure. The results of these analyses and the values for the six amino acids previously determined are given in Table I, together with the range of values for the amino acids in other eukeratins as cited by Block and Bolling.7 The nitrogen content of the amino acids determined accounts for 98.3 per cent of the total nitrogen of the protein.

Studies of the proteins, peptides and free amino acids of mature bovine enamel

“…25-30% collagen, very many carefully prepared teeth must be utilized. The use of samples that are either of inadequate size, or not completely free of dentine or cementum, combined with extensive dialysis of material that is largely diffusible, has in the past resulted in either the recovery of insufficient amounts ofmaterial for even a single amino acid analysis (Piez, 1962), or the recovery of collagen-like proteins, presumably from the adjacent tissue layers (Hess, Lee & Neidig, 1953;Stack, 1954;Battistone & Burnett, 1956;Rodriguez & Hess, 1963).…”

Mammalian Enamel Formation

“…Early efforts to define the amino acid composition of human enamel proteins isolated the insoluble protein components of decalcified mature human enamel [51][52][53]. These studies used the various microbiologic methods available at the time [51,53] or paper chromatography [52], to roughly define the enamel amino acid composition.…”

“…These studies used the various microbiologic methods available at the time [51,53] or paper chromatography [52], to roughly define the enamel amino acid composition. However, because of the mature stage of the enamel used in these studies, most of the enamel proteins, as we know them today, were not characterized.…”

EDTA soluble protein of human mature normal enamel

“…and 42%, respectively [2-4]. Citrate and lactate ions are also present in microquantities [5], whereas only traces of carbohydrate have been detected [6].Many studies have reported amino acid compositions for the human enamel matrix [7][8][9][10][11][12][13][14]. The main amino acids described were alanine, glutamic acid, glycine, proline, and serine.…”