Dicarboxylic Amino Acids Research Articles

GLUCOSURIA AND UNUSUAL AMINOACIDURIA

The association of glucosuria and aminoaciduria in the absence of other aspects of Fanconi's syndrome is rare. We have studied a kindred in which the proband was an asymptomatic 17 yr. old male referred with glycosuria. He was found to have renal glucosuria, but excretion and tubular reabsorption of phosphate, bicarbonate excretion, concentrating and acidifying ability, GFR, protein excretion, bone radiographs and physical examination were normal. Urinary losses of most neutral and dibasic amino acids were increased 1.5-6 fold generally reflecting an exaggeration of the normal pattern, but of considerable interest are the normal renal clearances and excretions for proline, the dicarboxylic amino acids (glutamate & aspartate), methlonine & isoleucine. Other proximal tubular functions and GFR were normal in family members. There were fewer abnormally excreted amino acids, and in generally lesser amounts, in father and sibs 2&3 than in the proband. In all siblings, the severity of aminoaciduria correlated with the degree of glucosuria and with age. The association of these abnormalities in this family suggests dominant inheritance of glucosuria from the mother and aminoaciduria from the father.

Structural glycoprotein from the media of pig aorta. Aggregation of the S-carboxamidomethyl subunits

Media of pig aorta was extracted with 1 M NaCl and 2 M MgCl2 to remove most of the soluble collagen, proteoglycans and glycoproteins. The glycoproteins remaining in the residue were extracted with 6 M urea-0.1 M mercaptoethanol. The urea soluble proteins were precipitated by dialysis, redissolved in 4 M guanidine-0.05 M DTT and were S-carboxamidomethylated (CM-guanidine extract). This extract was further fractionated by a variety of methods in order to separate a glycoprotein from collagen and proteoglycans. Caesium chloride density-gradient ultracentrifugation of the CM-guanidine extract separated a minor proteoglycan peak from a major glycoprotein fraction still containing some hydroxyproline. This major glycoprotein fraction was excluded as a single peak from Sephadex G 100 and G 200 in 4 M guanidinium chloride or in 6 M urea-0.2 per cent SDS. Sodium dodecylsulphate gel electrophoresis separated this high molecular weight Sephadex fraction into a major low molecular weight (approximately 35000 daltons) component and a minor high molecular weight component. This glycoprotein fraction could also be separated from a collagenous fraction and from proteoglycans by ion exchange chromatography on DEAE cellulose or by gelfiltration on Sepharose 4 B in 6 M urea-0.02 M EDTA-0.2 per cent SDS at pH 7.0. The isolated glycoprotein fraction is rich in dicarboxylic amino acids, contains galactose, mannose, (glucose), N-acetylglucosamine and sialic acid. The S-carboxamidomethyl glycoprotein preparation interacts with acid soluble calf skin collagen on isoelectric focusing in sucrose gradient in urea. This interaction is in favour of the biological role claimed for structural glycoproteins during fibrogenesis and differentiation.

Factors affecting the proteolytic degradation of elastin.

Studies in our laboratory have been concerned with aspects of the interaction of elastin with pancreatic elastase in efforts to assess intrinsic and extrinsic factors which might be involved in the regulation of elastolysis in vivo. Previous studies by others have clearly shown that elastase-elastin interactions are principally governed by ionic forces distributed between the cationic enzyme and the presumably anionic substrate. Our studies have now shown that most of the dicarboxylic amino acids in elastin are amidated, rendering elastin a cationic protein containing very few negatively charged side chains. Further, we have demonstrated that elastin can be rendered highly anionic by complex formation with amphiphilic agents such as fatty acids, bile salts, and detergents. These complexes are much more susceptible to elastolysis than elastin, itself. Evidence has also been obtained that these agents induce conformational changes in insoluble elastin, reflected in losses in elasticity of elastic fibers. Additional studies have shown that the formation of sedimentable elastin-elastase complexes seem not only to be unrelated, but, possibly, counterproductive to peptide bond scission in elastin. Further, both elastolysis and enzyme binding relationships are markedly influenced by calcium ions and by amphiphilic elastin ligands.

ChemInform Abstract: AMINODICARBOXYLIC ACIDS. PART XI. A SIMPLE METHOD FOR PREPARATION OF β‐BRANCHED ASPARTIC ACIDS

Chemischer InformationsdienstVolume 7, Issue 45 Preparative Organic Chemistry ChemInform Abstract: AMINODICARBOXYLIC ACIDS. PART XI. A SIMPLE METHOD FOR PREPARATION OF β-BRANCHED ASPARTIC ACIDS M. BOCHENSKA, M. BOCHENSKASearch for more papers by this authorJ. F. BIERNAT, J. F. BIERNATSearch for more papers by this author M. BOCHENSKA, M. BOCHENSKASearch for more papers by this authorJ. F. BIERNAT, J. F. BIERNATSearch for more papers by this author First published: November 9, 1976 https://doi.org/10.1002/chin.197645209Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue45November 9, 1976 RelatedInformation

Absorption, utilization, and safety of aspartic acid.

The dicarboxylic amino acids, asparate and glutamate, occupy unique positions in intermediary metabolism, particularly in the mitochondria, where they play important roles in nitrogen and energy metabolism. Administration of large quantities of glutamate and asparate to the newborn mouse produces a variety of neurotoxic effects, the most marked of which is neuronal necrosis. Neurotoxic effects of glutamate and aspartate in animal species other than the rodent are highly controversial. In the most critical animal species, the infant subhuman primate, at least four research groups have failed to duplicate the original report of glutamate-induced neuronal necrosis. Marked elevations in plasma glutamate or aspartate must occur for development of neuronal necrosis. In the highly sensitive neonatal mouse, plasma glutamate plus plasma aspartate levels must reach 60-80 mumol/dl to produce even minimal neuronal necrosis. In the healthy neonatal primate, loads producing plasma glutamate levels ranging from 50 to 1,600 mumol/dl failed to produce neuronal necrosis in our studies. Thus, it is clear that (1) marked elevations in plasma glutamate and aspartate must occur for neuronal necrosis, and (2) threshold levels required to produce neuronal necrosis vary greatly with species. The available data indicate little danger to the healthy primate and humans from ingestion of the dicarboxylic amino acids under anything resembling a reasonable intake. However, there is no doubt that these amino acids are toxic to the neonatal mouse at high dose levels.

Isolement et caracterisation de deux subunites constitutives des glycoproteines destructure du tissu sous cutane de lapin

Isolation and characterization of two subunits from structural glycoproteins of rabbit dermis Structural glycoproteins have been extracted by 8 M urea from the insoluble residue remaining after collagenase digestion of rabbit dermis and purified by Sepharose 4 B chromatography. After reduction and alkylation, Dowex 1 × 2 chromatography allowed separation of two structural glycoproteins (D 1 and D 2) in homogenous state as shown by chromatographic and electrophoretic behaviour as well as N terminal amino acid determination. These two glycoproteins have a molecular weight of about 16 000. Their amino acid compositions (very similar), are characterized by a high level of dicarboxylic amino acids and the absence of hydroxyproline and hydroxylysine. The less acidic glycoprotein (D 1) has glycine for N terminal amino acid and contains 10.4 percent of bound carbohydrates. The glycoprotein D 2 contains 5.1 percent of bound carbohydrates and its N terminal amino acid is glutamic acid.

1. Membrane vesicles of Escherichia coli K-12 CS7, a strain gentically derepressed for glutamate permease, maintain low aspartate transport activity, like that of prep.

1. Membrane vesicles of Escherichia coli K-12 CS7, a strain gentically derepressed for glutamate permease, maintain low aspartate transport activity, like that of preparations of the wild-type parent. Growth of the parent CS101 on aspartate as the source of carnon or nitrogen results in derepression of both asparatate and glytamate transport. Growth of strain CS7 on aspartate derepresses aspartate transport to the same extent as in strains CS101, but only slightly increases the derepressed level of glutamate transport activity. 2. The affinity of the membrane transport system for glutamate is enhanced by sodium, while that for asparate is not. 3. Although the affinities for glutamate (23 muM) and aspartate (12 muM) are similar, aspartate does not inhibit glutamate transport, while glutamate competitively inhibits aspartate transport. 4. Aspartate transport, but not glutamate transport, is competitively inhibited by C4 dicarboxylic acids, whereas 2-oxoglutarate competitively inhibits glutamate transport, but not aspartate transport. 5. Competitive inhibition of L-aspartate transport by L-glutamate and by the 5-methyl ester of L-glutamate is abolished in the presence of 2-oxoglutarate. However, 2-oxoglutarate does not affect the competitive inhibition of L-aspartate transport by D-aspartate and by DL-threo-3-hydroxyaspartate. The relationship between the two dicarboxylic amino acid transport systems and the spatial characteristics of the aspartate carrier are discussed in the light of these findings.

Amidated carboxyl groups in elastin

Dicarboxylic amino acids constitute the most numerous residues of insoluble elastin which are potentially ionizable in the physiological range of pH. These residues are essential in facilitating productive electrostatic interaction between elastase and elastin. The present study has investigated the possibility that the glutamic and aspartic acid residues of elastin are amidated. Acid-labile amide-bound ammonia of elastin was quantitated after hydrolysis of the insoluble protein with 2 M HCl by incubating aliquots of microdistilled hydrolysates with glutamate dehydrogenase, excess α-ketoglutarate, and reduced nicotinamide adenine dinucleotide and measuring the resultant decrease in A 340 due to oxidation of the dinucleotide cofactor. It was found that ligament elastin purified by repeated autoclaving contains approximately 2.29 μmol of acid-labile amide nitrogen per 10 mg of protein, a value equivalent to approximately 70% of the total number of dicarboxylic amino acid residues. Independent analysis of the amide content was obtained by amino acid analysis of an esterified and reduced elastin sample in which the free dicarboxylic amino acid residues had been converted to the corresponding alcohol derivatives. This analysis indicated that autoclaved ligament elastin contains approximately 18 glutamine, 3 asparagine, 4 glutamic acid and 5 aspartic acid residues per 1000 residues, in good agreement with the analysis of total acid-labile ammonia. The esterified and reduced elastin derivative was nearly inert as an elastase substrate, consistent with a lack of free dicarboxylic amino acid residues. However, addition of sodium dodecyl sulfate to this elastin derivative restores enzyme-substrate charge complementarity, and elastin-ligand complex was readily hydrolyzed by elastase at the fully stimulated rate, emphasizing the control such ligands can exert in elastolysis. The amide bonds of elastin were found to be significantly more resistant to hydrolysis by 0.1 M NaOH at 98 °C than were those of lysozyme or free amidated amino acids. The finding that most of dicarboxylic amino acid residues of elastin exist as neutral amides further emphasizes the apolar character of elastin and has bearing upon the metabolic susceptibility, ligandbinding ability and structural aspects of this connective tissue protein.

Peptides from pigeon cerebrum: Two-dimensional fingerprinting and amino acid analysis

The number and heterogeneity of endogenous peptides from pigeon cerebrum were studied by two-dimensional peptide fingerprinting. A highly consistent pattern of 8–9 peptides in the 1000–5000 molecular weight range was obtained from each cerebral sample. Amino acid analysis of the peptide material indicated that 30% of the identified residues were dicarboxylic amino acids and 30% were aliphatic amino acids. There was no evidence for the presence of arginine or half-cystine in the peptide fraction.

Inactivation of aspartate aminotransferase during transamination with chloropyruvate. Evidence against modification of Cys 390 in cytosolic isoenzyme

Both the cytosolic and mitochondrial isoenzyme of aspartate aminotransferase from pig heart were inactivated during transamination with chloropyruvate. Inactivation occurred with L-alanine as the amino group donor in the presence of potassium formate. When L-glutamate or L-aspartate was employed as the amino group donor in the transamination reaction with chloropyruvate, no inactivation occurred. This is in contrast to the case of inactivation by bromopyruvate (Okamoto, M. & Morino, Y. (1973) J. Biol. Chem. 248 , 82–90) where these natural dicarboxylic amino acid substrates were effective in the transamination reaction leading to syncatalytic inactivation (Birchmeier, W. & Christen, P. (1974) J. Biol. Chem. 249 , 6311–6315). The Cys 390 in the cytosolic isoenzyme which was modified in the syncatalytic inactivation was not modified under the present condition for inactivation with either chloropyruvate or bromopyruvate.

Differentiation of L-aspartate and L-glutamate high-affinity binding sites in a protein fraction isolated from rat cerebral cortex.

THE possibility that L-glutamate and L-aspartate are excitatory transmitters in the CNS is supported by neurochemical and neurophysiological evidence1. The problems of identifying particular synapses that are excited by one or the other of these dicarboxylic amino acids, and distinguishing between the two receptors are, however, more difficult. At the recent International Meeting of Neurochemistry (September 1975) Graham summarised some of the evidence favouring distinct functions for the two amino acids, concentrating on the possible transmitter role of L-aspartate. For example, a higher content of this amino acid is found in the ventral than in the dorsal grey matter of the spinal cord2, aortic occlusion leads to loss of aspartate content and degeneration of small neurones3, reduction in aspartate content is seen in the spinal cord after section of dorsal roots4 and in the olfactory cortex after olfactory bulbectomy5, which also decreases glutamate. Renshaw cells are slightly more sensitive to the ionotophoretic administration of L-aspartate while the reverse is true of interneurones of the dorsal spinal horn6. It is possible that L-glutamate and L-aspartate, being flexible molecules, fold or unfold and could interact with either receptor and McCulloch et al.7 accordingly used kainate, a conformational restricted analogue of glutamic acid, which would be unlikely to fold to occupy the aspartate receptor, and N-methyl-D-aspartate, which would be too small to interact with the glutamate receptor (Fig. 1). The difference in sensitivity between the two groups of neurones to these agonists was much greater: the Renshaw cells were much more sensitive to N-methyl-D-aspartate and the dorsal interneurones to kainate7.

ChemInform Abstract: STEREOSELECTIVITY AND PROTON BINDING IN COPPER(II) COMPLEXES OF ASPARTIC ACID, GLUTAMIC ACID, AND SOME N‐METHYL OR N‐BENZYLHISTIDINE DERIVATIVES

Stability constants and stereoselective effects are measured for copper(II) complexes with aspartate (asp), glutamate (glut), histidinate (his) and some N-alkylhistidinate derivatives: N-methyl- (mhis), N,N-dimethyl- (dimhis) and N-benzylhistidinate (bhis). For the dicarboxylic amino acids the predominant species in solution are CuA, CuHA and CuA2 *; for histidine and its derivatives:CuA, CuHA, CuA2 and CuHA2. By comparison of competition constants (vide infra) it is found that the ligand is bound via its glycine-locus in all complexes CuHA. For complexes CuHA2, the mono-protonated ligand, HA, is also bound to copper by its glycine-locus if A = his and bhis, and mainly so if A = mhis, but, if A = dimhis, HA, possibly, is monodentate and bound to copper by its imidazole group. No stereoselective effects are found in complexes CuA2 for A = asp, glut, his and mhis; for A = dimhis a significant positive effect (i.e. in favour of the meso complex Cu(DA)(LA)) is found, in contrast to the case for A = bhis. In the protonated copper complexes CuHA2, small negative effects are found for A = his, mhis and bhis, but no effect for dimhis.

Effects of glutamate, aspartate, and two presumed antagonists on feline rubrospinal neurones

The actions of dicarboxyl amino acids (GLUT, ASP, DLH) and of presumed amino acid antagonists (GDEE, HA 966) were studied in rubrospinal neurones with microelectrophoretic techniques. ASP and GLUT depolarized reversibly the cell membrane and increased its conductance. ASP had slightly stronger actions than GLUT. DLH had strong depolarizing actions without a clearcut change in membrane conductance; this may be due to the fact that DLH effects do not involve synaptic receptors. A specific action as antagonists for GLUT could not be shown for GDEE or HA 966. HA 966 effects were often accompanied by apparent postsynaptic actions. GDEE antagonized DLH effects sometimes even stronger than GLUT effects. The effects of GLUT and ASP are in principal agreement with a function as excitatory transmitters. The demonstration of a role as transmitter substances in excitatory (e.g. corticorubral or interpositorubral) pathways, however, still awaits the specific pharmacological antagonist.

COMPARATIVE CHEMOSENSITIVITY TO AMINO ACIDS AND THEIR ROLE IN THE FEEDING ACTIVITY OF BATHYPELAGIC AND LITTORAL CRUSTACEANS.

1. Feeding response exhibition in five marine crustaceans was observed in the presence of a range of concentrations of an amino acid mixture composed of equal parts DL alpha arnino-n-butyric acid, L-glutamic acid and taurine. Gnathophausiaingens, Pleuroncodes planipes, and Cancer antennarius displayed behavioral thresh olds of between 10-10 and 10-12 M; Spirontocaris taylori and Pagurus hirsutiusculus displayed thresholds between 10-7 and 10-9 M. 2. Electrophysiological response thresholds to the amino acid mixture were examined in G. ingens and C. antennarius. The antennular and dactyl receptors of G. ingens displayed thresholds of 10-7 and 10-8 M respectively. Maxilliped and dactyl receptors of C. antennarius both displayed a threshold of 5 x 10-5 M. 3. Panulirus interruptus antennule receptors displayed a degree of specificity to mono- and dicarboxylic amino acids.

Glyceraldehyde-3-phosphate dehydrogenases from Euglena gracilis: Purification and physical and chemical characterization

NAD +-dependent and NADP +-dependent glyceraldehyde-3-phosphate (G-3-P) dehydrogenases were isolated from Euglena gracilis and characterized as to their physical and chemical parameters. NAD +-G-3-P dehydrogenase was found to have a strong resemblance to similar enzymes from muscle tissue. It has a molecular weight of about 140,000, four subunits of identical size and charge, and a single species of NH 2-terminal amino acid. Two sulfhydryl groups per subunit are present, one of which is directly involved in the catalytic activity and is rapidly titratable. The enzyme also exhibits the “half the sites reactivity” of sulfhydryl groups as defined by O. P. Malhotra and S. A. Bernhard ((1968) J. Biol. Chem. 243, 1243). The pH and temperature optima are also similar to those of the enzymes from muscle tissue, as are the reaction kinetics and the strict specificity for NAD +. NADP +-dependent G-3-P dehydrogenase is different in many respects. Its molecular weight is slightly lower (~136,000) than that of the NAD + enzyme, though it also consists of four subunits. It has a higher affinity for the reverse reaction substrates, in line with its probable function in vivo in CO 2 fixation. There is only one sulfhydryl group per subunit, and that is not involved in activity, suggesting a difference in reaction mechanisms between the two enzymes. The NADP +-dependent enzyme exhibits activation by ATP, whereas the NAD +-dependent enzyme is competitively inhibited by this nucleotide. The greatest difference observed is in the physical characteristics of the enzymes. NADP +-G-3-P dehydrogenase was highly hydrophobic. Its solubility in a 10% aqueous solution of p-dioxane was approximately four to five times that of the NAD +-enzyme. Isolation of the enzyme was accomplished by fractionation in 1,2-dimethoxyethane, which also stabilized the enzymatic activity, as did aqueous p-dioxane. The high axial ratio of the NADP +-enzyme (~9) coupled with its very low degree of hydration as well as the high degree of amidation of the dicarboxylic amino acids (>90%) indicates that the exterior of the enzyme molecule is probably hydrophobic in nature. This is in agreement with its in vivo hydrophobic environment in the chloroplast membrane and explains the lability of the enzyme once extracted into an aqueous environment as well as its stabilization in solvents.

Evidence for three glutamic acid transporting systems with specialized physiological functions in [formula omitted

A set of three glutamate uptake systems with different specificities and regulatory properties allows the wild-type yeast Σ1278b to use external glutamate for different functions under different physiological conditions. One of these uptake systems is the general amino acid permease. The two other systems transport dicarboxylic amino acids with much higher specificity. One of them is constitutive in cells grown on NH 4 +; its activity is inhibited in washed cells coming from a growth medium containing glutamate and NH 4 + simultaneously. The rate of synthesis of the third permease is strongly reduced in the presence of NH 4 +, except in gdhA − mutants. In cells grown on glutamate, the formation of this system is not affected, but its activity is inhibited.

Dicarboxylic acid transport in membrane vesicles from Bacillus subtilis

Membrane vesicles isolated from Bacillus subtilis W23 catalyze active transport of the C4 dicarboxylic acids L-malate, fumarate, and succinate under aerobic conditions in the presence of the electron donor reduced beta-nicotinamide adenine dinucleotide or the non-physiological electron donor system ascorbate-phenazine methosulfate. The dicarboxylic acids are accumulated in unmodified form. Inhibitors of the respiratory chain, sulfhydryl reagents, and uncoupling agents inhibit the accumulation of the dicarboxylic acids. The affinity constants for transport of L-malate, fumarate, and succinate are 13.5, 7.5, and 4.3 muM, respectively; these values are severalfold lower than those reported previously for whole cells. Active transport of these dicarboxylic acids occurs via one highly specific transport system as is indicated by the following observations. (i) Each dicarboxylic acid inhibits the transport of the other two dicarboxylic acids competitively. (ii) The affinity constants determined for the inhibitory action are very similar to those determined for the transport process. (iii) Each dicarboxylic acid exchanges rapidly with a previously accumulated dicarboxylic acid. (iv) Other metabolically and structurally related compounds do not inhibit transport of these dicarboxylic acids significantly, except for L-aspartate and L-glutamate. However, transport of these dicarboxylic amino acids is mediated by independent system because membrane vesicles from B. subtilis 60346, lacking functional dicarboxylic amino acid transport activity, accumulate the C4 dicarboxylic acids at even higher rates than vesicles from B. subtilis W 23. (v) A constant ratio exists between the initial rates of transport of L-malate, fumarate, and succinate in all membrane vesicle preparations isolated from cells grown on various media. This high-affinity dicarboxylic acid transport system seems to be present constitutively in B. subtilis W23.

5-Oxo-L-prolinase (L-pyroglutamate hydrolase). Purification and catalytic properties.

5-Oxo-L-prolinase, an enzyme that catalyzes the conversion of 5-oxo-L-proline (L-pyroglutamate; L-2-pyrrolidone-5-carboxylate) to L-glutamate coupled with the cleavage of ATP to ADP and Pi, has been purified about 1600-fold from rat kidney. Purification was carried out in the presence of 5-oxo-L-proline which protects the enzyme under a variety of conditions. An estimate of the molecular weight (about 325,000) was made by gel filtration on Sephadex G-200. K+ (or NH4+) and Mg2+ were required for activity. GTP, ITP, CTP, and UTP were much less active than ATP; dATP was 43% as active as ATP. ADP inhibited and addition of pyruvate kinase and phosphoenolpyruvate activated the reaction. The enzyme, which is protected during storage by dithiothreitol, is inhibited by p-hydroxymercuribenzoate, N-ethylmaleimide, and iodoacetamide. The apparent Km values for 5-oxo-L-proline and ATP are, respectively, 0.05 and 0.17 mM. The pH profile indicates a broad range of activity from about pH 5.5 to pH 11.2 with apparent maxima at about pH 7 and pH 9.7. The formation of Pi and glutamate was equimolar over a wide pH range. When the enzyme was incubated with ATP, Mg2+, K+, and L-2-imidazolidone-4-carboxylate or L-dihydroorotate, cleavage of ATP to ADP and Pi occurred, but no cleavage of the imino acid substrates was observed; when the enzyme was incubated under these conditions with 2-piperidone-6-carboxylate, 4-oxy-5-oxoproline, and 3-oxy-5-oxoproline, the corresponding dicarboxylic amino acids were formed, but the molar ratio of Pi to amino acid formation was significantly greater than unity.

Fractionation of human parotid salivary proteins and the isolation of an histidine-rich acidic peptide which shows high affinity for hydroxyapatite surfaces

Anion exchange chromatography of the proteins from litre quantities of parotid saliva has been shown to be a particularly appropriate technique for obtaining substantial amounts of the more acidic macromolecular components present in this secretion. One specific component obtained by this means was further purified by the use of gel permeation chromatography using a recycling technique. This material was remarkable for its high content of histidine ( 190 residues 1000 ) and arginine ( 111 residues 1000 ) and for its elevated levels of the dicarboxylic amino acids ( 233 residues 1000 ), particularly aspartate ( 144 residues 1000 ). A value for its minimum molecular weight, 4520, calculated from the amino acid composition, was in good agreement with the value of 4510 obtained by analytical ultracentrifugation. Its isoelectric point was found to be 7.04 at 20 °C and carbohydrate was absent. Interest in this component arises as a consequence of its high affinity for hydroxyapatite and dental enamel surfaces, suggesting a possible role for this material in the early stages of the formation of the acquired enamel pellicle.

A new dicarboxylic amino acid from seeds of Pentaclethra macrophylla

The title compound was isolated and shown by various physical and chemical techniques to be a new pyrrolidonecarboxylic acid.