The preparation of matrix-bound proteases and their use in the hydrolysis of proteins

Four proteases, crude acid protease from Aspergillus, pronase, amino-peptidase M, and prolidase, have been covalently attached to activated agarose and to amino propyl glass beads. The matrix-bound enzymes have been tested as catalysts for the complete hydrolysis of protein substrates, with the primary goal to isolate unstable amino acid derivatives present in the substrate protein. Under conditions used in the present work, the total amino acid release from the protease-catalyzed hydrolysis of four substrate proteins (pancreatic ribonuclease, egg white lysozyme, yeast enolase, and bovine insulin) was 95–103% of that observed in standard acid hydrolysis. Recovery of individual amino acids showed greater deviation from the theoretical values, but cystine was the only amino acid recovered in low yields (42–77%) from all four proteins. Derivatized amino acids, such as methionine sulfoxide, O-(butylcarbamoyl)-serine, and N-glycosyl asparagine have been obtained from chemically modified proteins or from unmodified glycoprotein in good yield, and normal amino acid constituents of proteins which cannot be quantified after acid hydrolysis (tryptophan, asparagine, and glutamine) have also been determined either directly after proteolysis or after proteolysis in conjunction with acid hydrolysis.     

Amino acids,sugars and sterols of some Mediterranean brown algae

Free amino acids, amino sulfonic acids, sugars and sterols have been examined and quantitatively determined in 10 brown seaweeds. Acidic amino acids and their amides are the main components of the amino acid fraction. Cysteinolic acid, taurine and its N-methyl derivatives have been identified in most of the species examined. In all the algae, mannitol is present, sometimes in very large amounts. The sterol fractions of all the species contain fucosterol, cholesterol and 24-methylenecholesterol; minute amounts of 22-dehydrocholesterol and 24-methylcholesta-5, 22-dien-3β-ol have also been frequently detected.     

Free amino acids and γ-glutamyl peptides in seeds of Fagus silvatica

The contents of amino acids and peptides have been investigated in seeds of Fagus silvatica L. (beechnuts). In addition to the common amino acids, the following compounds have been isolated and identified: 4-hydroxyproline (probably the cis-l-isomer), N⁵-acetylornithine, 3-(2-furoyl)-l-alanine, methionine sulfoxide (probably an artefact), pipecolic acid (probably partially racemized d-isomer), l-willardiine (with a small amount of the d-isomer), N-(3-amino-3-carboxypropyl)azetidine-2-carboxylic acid, N-[N-(3-amino-3-carboxypropyl)-3-amino-3-carboxypropyl]azetidine-2-carboxylic acid, 2(S),5(S),6(S)-5-hydroxy-6-methylpipecolic acid, 2(S),5(R),6(S)-5-hydroxy-6-methylpipecolic acid, γ-glutamylalanine, γ-glutamylglutamic acid, γ-glutamylisoleucine, γ-glutamylleucine, γ-glutamylmethionine sulfoxide (probably an artefact), γ-glutamylphenylalanine, γ-glutamyltyrosine, γ-glutamylvaline, glutathione, γ-glutamylwillardiine, and γ-glutamylphenylalanylwillardiine. γ-Glutamylphenylalanine and willardiine are the dominating components of the amino acid fraction.The isolations were performed by use of ion exchange chromatography, taking advantage of the different pK-values of the amino acids, mainly on acid resins in the 3-chloropyridinium form with aq. 3-chloropyridine as eluant and on basic resins in the acetate form with aqueous acetic acid as eluant. These methods in combination with preparative paper chromatography have permitted the isolation and identification of compounds present in amounts as low as 1/6000 of the dominant ninhydrin-reactive component. The implications of the occurrence of this large variety of compounds in the Fagaceae are briefly discussed.     

Formation of specific amino acid sequences during thermal polymerization of amino acids

The mechanism of the thermal polymerization (at 180°C) of glutamic acid, tyrosine, and glycine has been studied. Glutamic acid is quickly and almost completely converted into pyroglutamic acid. The only dipeptide that is formed by dimerization of the remaining two amino acids is cyclic glycyl-tyrosine (a diketopiperazin). In a secondary reaction pyroglutamic acid interacts with cyclic glycyl-tyrosine and yields pyroglutamyl-glycyltyrosine and pyroglutamyl-tyrosyl-glycine. Other di- or tripeptides are not observed. The preferential appearance of the two pyroglutamyl-peptides has been reported earlier by Nakashima et al. (1977). The present data explain those results. Model experiments show that cyclic glycyl-tyrosine can also be cleaved by other acids or bases. In the presence of acetic acid at 118°C N-acetyl-glycyl-tyrosine is the major product. Partial hydrolysis predominantly yields tyrosyl-glycine. These effects are explained by stereospecific interactions. The results on self-ordering of amino acids during peptide formation are discussed in respect of the origin of prebiotic enzymes and genetic information.     

Reverse-phase purification and silica gel thin-layer chromatography of porphyrin carboxylic acids

Thin-layer chromatography on silica gel 60 plates in the solvent N,N-dimethylformamide/methanol/ethylene glycol/glacial acetic acid/1-chlorobutane/chloroform (4/35/6/0.4/18/20 by volume) separates porphyrin carboxylic acids by the number of free carboxyl groups. Coproporphyrins I and III and isocoproporphyrin are separated in 30 min, other porphyrins in 15 min. The N,N-dimethylformamide and acetic acid in the solvent strongly increase porphyrin fluorescence on the plates. Fading and diffusion of the fluorescent patterns is prevented by storage of the plates in the cold and dark without oxygen and with desiccant. In a preliminary step, porphyrins are purified in high yields, concentrated, and deacidified rapidly (2 min) by reversephase chromatography on cartridges containing a C₁₈ spacer or on Amberlite XAD-2 columns. The methods are applied to urines of porphyria patients and for following porphyrin ester hydrolysis.     

Free amino acids in some sponges

Most invertebrates, particularly those of marine origin, have relatively high concentrations of free amino acids which are considered an important constituent of their osmoregulatory mechanisms [1]. Very little information is available on the free amino acid distribution in Porifera [2,3]. Common amino acids in some sponges were recognised by paper chromatography by Inskip and Cassidy [4] and Ackermann et al. [5,6] included a few sponges in their survey of the occurence of nitrogen compounds in marine invertebrates. More recently Bergquist and Hartman [7] surveyed semiquantitatively the distribution of free amino acids in several sponges. In the present paper we report on the amino acid composition of 12 species of sponges belonging to the class Demospongiae as a part of a study on the metabolites of Porifera [8]. Fresh sponges were extracted with aqueous ethanol. The organic solvent was removed and the aqueous solution, after removal of the ether soluble compounds, was separated into cationic, anionic and neutral fractions by ion-exchange chromatography. The cation fraction was analysed for amino acids using an automatic amino acid analyser. The results, which are presented in Table 1, show that all species of sponges examined have a similar composition in common amino acids. Glycine almost always appears as the dominant protein amino acid, followed by high concentrations of alanine and glutamic acid, whereas relatively lower concentrations of basic amino acids are present. In Axinella cannabina, Chondrosia reniformis, Chondrilla nucula, Cliona viridis and Hymeniacidon sanguinea, glycine represents more than 77% of the total amino acids. The high percentage of free glycine (90.4%) in Chondrosia reniformis is noteworthy. The anionic and the neutral fractions were examined for sulfur-containing amino acids using PC. Taurine (Table 2) was detected in all the Porifera examined; this is in agreement with previous observations [5–7]. N-Methyltaurine was identified in some of the species examined, whereas neither N,N-dimethyltaurine nor N,N,N-trimethyltaurine were found.     

Analysis of adipimidate-crosslinked lysine

The chromatographic conditions for separation of N,N′-bislysyl(?-N)adipamidine and N-lysyl(?-N)adipamidinic acid, which were the products of acid hydrolysis of proteins treated with adipimidate esters, from other amino acids on an amino acid analyzer were established including their ninhydrin color values. Kinetics of decomposition of these lysine derivatives under the conditions of total acid hydrolysis of protein are also reported.     

Transformation of 3-(3-carboxyphenyl)alanine in iris species An example of diversity in catabolism of secondary plant products

3-(3-Carboxyphenyl)-DL-[2-¹⁴C]alanine has been incorporated into four species of iris. In all species extensive metabolization takes place. In Iris × hollandica, in which both the alanine derivative and 3′-carboxyphenylglycine occur, the products identified are the glycine derivative, 3′-carboxyphenylacetate acid, 3′-carboxymandelic acid, and 3′-carboxyphenylglyoxylic acid. In I. sanguinea, in which the alanine and glycine derivatives also occur, the products identified are the glycine and acetic acid derivatives but the major product is 3-(3-hydroxymethylphenyl)alanine, a naturally occurring amino acid in this species. In I. tectorum, in which only the carboxy-substituted alanine derivative occurs, the products identified are the acetic acid and glyoxylic acid derivatives. In I. pallida, not containing any of the meta-substituted amino acids, the products identified are again the acetic acid and glyoxylic acid derivatives. The results have been further substantiated by incorporation of labelled 3′-carboxyphenylacetic acid and 3′-carboxymandelic acid into I. × hollandica and I. sanguinea.The results demonstrate three different metabolic patterns for the alanine derivative and confirm previous results on the pathway from the alanine to the glycine derivative. Furthermore, the results may be of significance for the elucidation of the catabolism of phenylalanine.     

Amino acids and low-molecular-weight carbohydrates of some marine red algae

Amino acids and low-MW carbohydrates of 18 red algae have been analyzed. Several non-protein amino acids have been identified, including pyrrolidine-2,5-dicarboxylic acid (3c) and N-methylmethionine sulfoxide (5), new natural products, and 13 known compounds, citrulline, β-alanine, γ-aminobutyric acid, baikiain (1), pipecolic acid (2), domoic acid (3a), kainic acid (3b), azetidine-2-carboxylic acid (4), methionine sulfoxide taurine, N-methyltaurine, N,N-dimethyltaurine and N,N,N-trimethyltaurine. Sugars present were mainly floridoside, isofloridoside and mannoglyceric acid. Details of the structural elucidation of new compounds are also given.     

Specificity and stereospecificity of α-chymotrypsin

1. The optically pure p-nitrophenyl esters of the d and l enantiomers of N-acetyl-tryptophan, N-acetylphenylalanine and N-acetyl-leucine, and the p-nitrophenyl ester of N-acetylglycine, have been prepared. 2. These materials are all substrates of α-chymotrypsin, and the rates of deacylation of the corresponding acyl-α-chymotrypsins have been determined. 3. As the size of the amino acid side chain increases, the l series deacylate progressively faster than the N-acetylglycyl-enzyme, and the d series progressively more slowly. 4. The results are interpreted in terms of a three-locus model of the enzyme's active site, which accounts for the interrelationship between substrate specificity and stereospecificity observed. 5. The concepts of negative specificity and of specificity saturation are introduced.     

A procedure for the rapid, quantitative N-acetylation of amino sugar methyl glycosides.

A rapid and quantitative procedure is described for the re-N-acetylation of amino sugar methyl glycosides prior to their analysis by gas-liquid chromatography. Two equivalents of pyridine are added to acidic methanolysates containing amino sugars, serving both to neutralize the acid and to act as a catalyst for the subsequent N-acetylation reaction with acetic anhydride. The N-acetylation is quantitative and complete within 10 min at ambient temperature. Excess acetic anhydride is destroyed by solvolysis with the methanolic solvent. The procedure has been used effectively for methanolysates containing 0.01–2.0 mg/ml glucosamine. The procedures utilizing ion-exchange columns and insoluble salts are thus circumvented and all reaction byproducts are volatile. The procedure is therefore ideally suited for the simultaneous workup of numerous samples for analytical procedures such as gas-liquid chromatography.     

Oxidative addition of the C-O bond of amino acid esters to Rh(I) forming chelating acyl complexes

Esters of N-acylated amino acids and the sterically demanding phosphine 2-(di-ortho-tolylphosphino)phenol react within 1 h at room temperature with the Rh(I) centers of [Cl(μ-Cl)Rh(cyclooctene)₂]₂ to give products of oxidative addition of the ester carbonyl-O bond. The N-acyl carbonyl oxygen is bound to the Rh in these initial adducts, but is displaced upon addition of PMe₃, PhPMe₂, NH₂NMe₂, or the thioether function of a methionine derivative. Remarkably, both initial products from achiral amino acids and their ligand adducts are formed as single five-coordinate diastereomers in essentially quantitative yields. However, asymmetric induction by chiral amino acid derivatives of proline and phenylalanine on the stereochemistry at Rh was modest. Finally, the identities of infrared absorptions of acyl and amide groups in the complexes were established unequivocally by synthesis and spectroscopy of N-acetylglycine esters with a ¹³C label at either the ester or amide carbonyl group.     

Decomposition in presence of nitrate of amino acids,especially tyrosine,during acid hydrolysis of plant material and standard amino acid solution

Summary Nitrate present in or added to ryegrass samples considerably decomposed tyrosine during hydrolysis. Addition of 30 mg stannous chloride to 250 mg ryegrass in 250 ml 6N HCl had only a small preventing effect, whereas 480 mg SnCl₂.2H₂O or 0.17 ml thioglycollic acid, entirely prevented decomposition. Other amino acids remained unaffected by nitrate. Additions of nitrate to standard amino acid solutions completely decomposed tyrosine. Other amino acids, except proline, progressively decomposed with increasing nitrate additions. Effects from stannous chloride and thioglycollic acid were the same as on ryegrass     

Diversity of the Lactic Acid Bacterium and Yeast Microbiota in the Switch from Firm- to Liquid-Sourdough Fermentation

Four traditional type I sourdoughs were comparatively propagated (28 days) under firm (dough yield, 160) and liquid (dough yield, 280) conditions to mimic the alternative technology options frequently used for making baked goods. After 28 days of propagation, liquid sourdoughs had the lowest pH and total titratable acidity (TTA), the lowest concentrations of lactic and acetic acids and free amino acids, and the most stable density of presumptive lactic acid bacteria. The cell density of yeasts was the highest in liquid sourdoughs. Liquid sourdoughs showed simplified microbial diversity and harbored a low number of strains, which were persistent. Lactobacillus plantarum dominated firm sourdoughs over time. Leuconostoc lactis and Lactobacillus brevis dominated only some firm sourdoughs, and Lactobacillus sanfranciscensis persisted for some time only in some firm sourdoughs. Leuconostoc citreum persisted in all firm and liquid sourdoughs, and it was the only species detected in liquid sourdoughs at all times; it was flanked by Leuconostoc mesenteroides in some sourdoughs. Saccharomyces cerevisiae, Candida humilis, Saccharomyces servazzii, Saccharomyces bayanus-Kazachstania sp., and Torulaspora delbrueckii were variously identified in firm and liquid sourdoughs. A total of 197 volatile components were identified through purge and trap–/solid-phase microextraction–gas chromatography-mass spectrometry (PT–/SPME–GC-MS). Aldehydes, several alcohols, and some esters were at the highest levels in liquid sourdoughs. Firm sourdoughs mainly contained ethyl acetate, acetic acid, some sulfur compounds, and terpenes. The use of liquid fermentation would change the main microbial and biochemical features of traditional baked goods, which have been manufactured under firm conditions for a long time.     

Azetidine-2-carboxylic acid derivatives from seeds of Fagus silvatica L. and a revised structure for nicotianamine

2(S),3′(S)-N-(3-Amino-3-carboxypropyl)azetidine-2-carboxylic acid and 2(S),3′(S),3″(S)-N-[N-(3-amino-3-carboxypropyl)-3-amino-3-carboxypropyl]azetidine-2-carboxylic acid have been isolated from seeds of Fagus silvatica L. (beechnuts). The structures have been established by PMR- and ¹³C-NMR-spectroscopy and by synthesis from l-azetidine-2-carboxylic acid. The second of the new amino acids is identical with nicotianamine. previously isolated from Nicotiana tabacum but assigned a different formula. The ring opening reactions of azetidine-2-carboxylic acid in neutral solution have been studied and the chemical and possibly biochemical precursor role of this amino acid for various amino acids including the two new ones described here, nicotianine [N-(3-amino-3-carboxypropyl)nicotinic acid] and methionine is discussed.     

Gas Chromatography-Mass Spectrometry-Based Metabolite Profiling of Salmonella enterica Serovar Typhimurium Differentiates between Biofilm and Planktonic Phenotypes

The aim of this study was to utilize gas chromatography coupled with mass spectrometry (GC-MS) to compare and identify patterns of biochemical change between Salmonella cells grown in planktonic and biofilm phases and Salmonella biofilms of different ages. Our results showed a clear separation between planktonic and biofilm modes of growth. The majority of metabolites contributing to variance between planktonic and biofilm supernatants were identified as amino acids, including alanine, glutamic acid, glycine, and ornithine. Metabolites contributing to variance in intracellular profiles were identified as succinic acid, putrescine, pyroglutamic acid, and N-acetylglutamic acid. Principal-component analysis revealed no significant differences between the various ages of intracellular profiles, which would otherwise allow differentiation of biofilm cells on the basis of age. A shifting pattern across the score plot was illustrated when analyzing extracellular metabolites sampled from different days of biofilm growth, and amino acids were again identified as the metabolites contributing most to variance. An understanding of biofilm-specific metabolic responses to perturbations, especially antibiotics, can lead to the identification of novel drug targets and potential therapies for combating biofilm-associated diseases. We concluded that under the conditions of this study, GC-MS can be successfully applied as a high-throughput technique for “bottom-up” metabolomic biofilm research.     

Initiation of ovalbumin synthesis in chicken oviduct magnum: Transient labeling of the NH2-terminus by methionine

The incorporation of [³⁵S]methionine into ovalbumin, a protein containing NH₂-terminal N-acetylglycine, has been studied in chicken oviduct magnum cells. The purification of [³⁵S]methionine-labeled ovalbumin from total oviduct proteins was accomplished by dialysis of a crude extract at pH 3.6 followed by chromatography on carboxymethyl cellulose. The radioactive ovalbumin eluted from the column in three peaks (P₀, P₁, and P₂-containing 0, 1, and 2 moles of phosphate, respectively, per mole of ovalbumin). The kinetics of labeling of peaks P₀ and P₁ showed that the ratio of radioactivity in NH₂-terminal methionine to total incorporation was greater at 2 min of labeling than at later times. The transient labeling of the NH₂-terminus of ovalbumin with methionine indicates that methionine is the initiator amino acid for the synthesis of this protein, which in its mature form contains NH₂-terminal N-acetylglycine.     

Free and bound phenolic acids of lucerne (Medicago sativa cv europe)

The distribution of free and covalently-bound phenolic acids was studied in various fractions obtained from fresh lucerne shoots. p-Hydroxybenzoic, vanillic, p-coumaric and ferulic acids were present, both free and bound, in all the fractions. Salicylic and sinapic acids occurred only in a bound, alkali-labile state and were found almost entirely in the ‘aqueous phase’ fraction after treatment of methanol-chloroform-water extract according to Bligh and Dyer. Many other common phenolics were absent. Amounts of the phenolic acids much larger than those extracted by methanol-chloroform-water were extracted subsequently by phenol-acetic acid-water and passed into the ‘diffusate’ fraction on dialysis of this extract against 70% acetic acid. Small, though significant, quantities of phenolic acids remained with the bulk protein in the ‘bag contents’ fraction. The extent to which the phenolic acids in these last two fractions are held to protein by covalent bonds or by secondary-valence attractions is discussed, particularly in relation to the isolation of N-feruloylglycylphenylalanine after partial hydrolysis. Suggestions are made for improving analytical procedures.     

Gas chromatographic assay of total and O-acetyl groups in bacterial lipopolysaccharides

An improved gas chromatographic method for the determination of total, i.e., amide- and ester-linked, acetyl groups in hydrolysates of bacterial lipopolysaccharides has been developed. After hydrolysis with 0.2 n HCl overnight at 100°C and adjustment of the hydrolysate to pH 3–4, 2 μl of the samples contalning 0–6 μg of acetic and 1–2 μg of propionic acid are directly injected into a gas chromatograph fitted with a 1.5-m glass column packed with Porapak QS. O-Acetyl groups can selectively be determined after hydrolysis with 0.05 n NaOH for 3–4 hr at room temperature and adjustment of the sample to pH 3–4. N-Acetyl groups can be calculated as the difference between total and O-acetyl. The above-mentioned phase allows quantitation of short-chain volatile fatty acids (S-C VFAs) up to n-valeric acid in a range of 0–6.0 μmol using an appropriate internal standard.     

Thermochemistry of N-C bonds hydrolysis in amides,peptides, N-acetyl amino acids and high-energy N-C bonds hydrolysis in N-acetyl imidazole and urea

• 1.1. The reaction enthalpies of hydrolysis of amides, peptides and N-acetyl amino acids were calculated for both ionized and un-ionized forms of reaction components.
• 2.2. The average values of reaction enthalpies of amides, peptides and N-acetyl amino acids hydrolysis were essentially different from each other for ionized forms of reaction components and were equal for un-ionized forms of reaction components in the error interval.
• 3.3. As an example of high-energy N-C bonds N-acetyl imidazol and urea were discussed. It was found that the reaction enthalpies of hydrolysis of above compounds were different from analogous thermodynamic values of hydrolysis of amides, peptides and N-acetyl amino acids for any forms of components.