Serine isolation

Comparison of the optical rotatory dispersion exhibited by O-/3-d-xylopyranosyl-L-serine isolated from glycosaminoglycans with those of the two synthetic anomers revealed that the natural material has the /3-D anomeric configuration.159 Moreover, the O-D-xylosyl-L-serine present in normal urine also has the /3-d configuration, as had earlier been suggested.190 The origin of the urinary compound is unknown, but it may be a catabolite of certain glycoproteins. 

Protein chemists had long felt the need for an absolute standard for amino acids. In 1950, D-(+)-glyceraldehyde was converted, by genetic change in five steps, to D-( + )-serine. This showed that the (—)-serine, isolated from the hydrolysis of proteins, was L-(—)-serine. This result helped to fix all the amino acids of protein as members of the L-family, although some (such as alanine) show the ( + ) rotation (Brewster a/., 1950). 

L-Serine isolated from a sulfuric acid hydrolyzate of sericine, a protein component of silk (lat. sericus silken) by E. Cramer. Structure by the same author. Synthesis E. Fischer and H. Leuchs, 1902. 

The amino group of threonine, like that of lysine, is not available for reversible transfer reactions. Thus, the from other amino acids is not found in threonine - and the C N ratio of threonine, like that of serine, isolated from body tissues, shows only small differences in the dilution of the two labels. The explanation for this is that the catabolism of threonine by way of glycine does not involve loss of the amino group. ... 

Later the complete structures of mycoside (M. butyricum) 189) and mycoside (M. scrofulaceum) 190) were reported. A similar structure proposed for mycoside C2 (M. avium) contained two puzzling features, i.e. the presence of palmitic acid as a fatty acid component instead of a C28 acid derivative and a pentapeptide backbone 191). N,0-dimethyl-L-serine, isolated from hydrolysates of two mycosides C 186) was most probably an artefact. The configuration of alaninol was determined by transformating it into alanine by chromic acid oxidation and further treatment with D-amino acid oxidase. The substance was not affected by the enzyme, showing that it was L-alaninol 191). 

ViLKAS, E., A. Rojas, and E. Lederer Sur un nouvel acide amine, la N-methyl O-methyl L-serine, isole des mycosides de Mycobacterium butyricum and M. avium. Compt. Rend. Acad. Sci. (Paris) 261, 4258 (1965). 

Me2NC5H5NCPh3 Cr, CH2CI2, 25°, 16 h, 95% yield. In this case a pri-maiy alcohol is cleanly protected over a secondary alcohol. The reagent is a stable isolable salt. If the solvent is changed from CH2CI2 to DMF, the amine of serine can be selectively protected. 

Madurastatins A1 (119 Scheme 11.17), A2 (120), A3 (121), B1 (122), and B2 (123) were isolated in 2004 from a clinical isolate of a pathogenic actinomycete, a strain of Actinomadura madurae [189]. The stereochemistry of the N-methyl-N-hydrox-yornithine residue remains unknown, but it was determined that the serine and aziridine residues are D, and the rest are L. 

Sirolimus (SRL), also termed rapamycin is a macrolide lactone isolated from the ascomycete species Stre-ptomyces hygroscopicus. After binding to its cytosolic receptor FKBP-12 the resulting complex inhibits the multifunctional serine-threonine kinase mTOR (mammalian target of rapamycin). Inhibition of mTOR prevents activation of the p70S6 kinase and successive... 

N -Fmoc serine benzyl ester 2, which could be prepared as shown or purchased commercially, was smoothly converted to the crystalHne O-methylthiomethyl (MTM) ether 3 in high yield via a Pummerer-Hke reaction using benzoyl peroxide and dimethyl sulfide in acetonitrile [39]. This common intermediate was used to synthesize both 5 and 8 [40]. Both Ogilvie [41] and Tsantrizos [42] had reported that I2 was an effective activator with similar MTM ether substrates. The H promoted nucleosidation reaction between O-MTM ether 3 and bis-silylated thymine 4 produced the nucleoamino acid 5 in 60% isolated yield (100% based on recovered 3). Hydrogenolytic deprotection of the benzyl ester with H2, Pd/C in MeOH gave the thymine-containing nucleoamino acid 6 in quantitative yield. 

The crystal structure of the HNL isolated from S. bicolor (SbHNL) was determined in a complex with the inhibitor benzoic acid." The folding pattern of SbHNL is similar to that of wheat serine carboxypeptidase (CP-WII)" and alcohol dehydrogenase." A unique two-amino acid deletion in SbHNL, however, is forcing the putative active site residues away from the hydrolase binding site toward a small hydrophobic cleft, thereby defining a completely different active site architecture where the triad of a carboxypeptidase is missing. 

Definition of Ej and E2 eonformations of the a subunit of Na,K-ATPase involves identification of cleavage points in the protein as well as association of cleavage with different rates of inactivation of Na,K-ATPase and K-phosphatase activities [104,105]. In the Ei form of Na,K-ATPase the cleavage patterns of the two serine proteases are clearly distinct. Chymotrypsin cleaves at Leu (C3), Fig. 3A, and both Na,K-ATPase and K-phosphatase are inactivated in a monoexponential pattern [33,106]. Trypsin cleaves the E form rapidly at Lys ° (T2) and more slowly at Arg (T3) to produce the characteristie biphasic pattern of inactivation. Localization of these splits was determined by sequencing N-termini of fragments after isolation on high resolution gel filtration columns [107]. 

Removal of the oligosaccharide chain from the glycoprotein usually involves the use of one of three main methods treatment with NaOH-NaBH4, hydrazinolysis, or proteolysis.34-36 The NaOH-NaBH4 treatment is used to release, somewhat specifically, oligosaccharides O-linked to serine and threonine. Hydrazinolysis is used to break N-linkages, and proteolysis, to isolate glycopeptides. Each method apparently still has some drawbacks. 

A murine male germ cell-assocated kinase (mak) was isolated by virtue of its weak homology to the v-ros tyrosine kinase (Matsushime et al., 1990). Although it was isolated because of its homology to a tyrosine kinase, sequence analysis revealed that it belongs to the serine/threonine... 

TV-Benzylidene dehydroalanine, however, could not be isolated by this method because the compound decomposed during work up at room temperature.[ 181 CDI was inert toward a series of dipeptides containing a serine residue in the TV-terminal position... 

The second method also relies on site-specific chemical modification ofphosphoproteins (Oda et al., 2001). It involves the chemical replacement of phosphates on serine and threonine residues with a biotin affinity tag (Fig. 2.7B). The replacement reaction takes advantage of the fact that the phosphate moiety on phosphoserine and phosphothreonine undergoes -elimination under alkaline conditions to form a group that reacts with nucleophiles such as ethanedithiol. The resulting free sulfydryls can then be coupled to biotin to create the affinity tag (Oda et al., 2001). The biotin tag is used to purify the proteins subsequent to proteolytic digestion. The biotinylated peptides are isolated by an additional affinity purification step and are then analyzed by mass spectrometry (Oda et al., 2001). This method was also tested with phosphorylated (Teasein and shown to efficiently enrich phosphopeptides. In addition, the method was used on a crude protein lysate from yeast and phosphorylated ovalbumin was detected. Thus, as with the method of Zhou et al. (2001), additional fractionation steps will be required to detect low abundance phosphoproteins. 

Serine/threonine kinase activity has been reported in ESP of pepsin-HCl isolated muscle larvae (Arden el al., 1997) and kinase activity was associated with proteins of 70 and 135 kDa. Phosphorylation status is functionally significant for multiple regulatory factors, including those involved in muscle differentiation (Li et al., 1992). Therefore, kinase activity in parasite secretions may be significant in either the muscle or intestinal phases of infection. 

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