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1. The preparation of stereospecifically tritiated glycines and the determination of their absolute configurations by the use of d-amino acid oxidase are described. 2. The reaction catalysed by serine transhydroxymethylase, which results in the conversion of glycine into serine, has been separated into at least four partial reactions. It is suggested that the first event in this conversion is the formation of a Schiff base intermediate of glycine and pyridoxal phosphate. The next important step involves the removal of the 2S-hydrogen atom of glycine to give a carbanion intermediate. Experiments pertinent to the mechanism of conversion of this carbanion intermediate into serine are described. 3. The enzyme preparation catalysing the conversion of glycine into serine also participates in the conversion of glycine into threonine and allothreonine. In both these conversions, glycine --> serine and glycine --> threonine, the 2S-hydrogen atom of glycine is eliminated and the 2R-hydrogen atom of glycine is retained. 4. In the light of these experiments the mechanism of action of serine transhydroxymethylase is discussed. It is suggested that methylenetetrahydrofolate is the carrier of formaldehyde, from which formaldehyde may be liberated at the active site of the enzyme, thus allowing the overall reaction to take place.

Over 9 million new active tuberculosis (TB) cases emerge each year from an enormous pool of 2 billion individuals latently infected with Mycobacterium tuberculosis (M. tb.) worldwide. About 3 million new TB cases per year are unaccounted for, and 1.5 million die. TB, however, is generally curable if diagnosed correctly and in a timely manner. The current diagnostic methods for TB, including state-of-the-art molecular tests, have failed in delivering the capacity needed in endemic countries to curtail this ongoing pandemic. Efficient, cost effective and scalable diagnostic approaches are critically needed. We report a multiplex TB serology panel using microbead suspension array containing a combination of 11 M.tb. antigens that demonstrated overall sensitivity of 91% in serum/plasma samples from TB patients confirmed by culture. Group wise sensitivities for sputum smear positive and negative patients were 95%, and 88%, respectively. Specificity of the test was 96% in untreated COPD patients and 91% in general healthy population. The sensitivity of this test is superior to that of the frontline sputum smear test with a comparable specificity (30–70%, and 93–99%, respectively). The multiplex serology test can be performed with scalability from 1 to 360 patients per day, and is amenable to automation for higher (1000s per day) throughput, thus enabling a scalable clinical work flow model for TB endemic countries. Taken together, the above results suggest that well defined antibody profiles in blood, analyzed by an appropriate technology platform, offer a valuable approach to TB diagnostics in endemic countries.

An improved method for the preparation of various species of porphobilinogen stereospecifically labelled with 3H in the side chains (at C-6, C-7 and C-8) is described. These labelled samples were used to study the mechanism and stereochemistry of anaerobic as well as aerobic coproporphyrinogen III oxidase of light-grown Rhodopseudomonas spheroides. It was shown that both the oxidases catalyse the conversion of the propionate side chains of coproporphyrinogen III into the vinyl groups of protoporphyrinogen IX, (formula; see text) with the labilization of the pro-S-hydrogen atom at the beta-position. These results are similar to those previously recorded for such conversions in animal and plant systems. In the light of the cumulative information available to date, mechanisms for the conversion, (formula; see text) are discussed and doubt is cast on the participation of hydroxylated intermediates in the process.

Cel5A of Thermotoga maritima, a 37 kDa cellulase of the family GH5, was expressed in partially soluble state in E. coli. However, the truncated version tCel5A1, produced by removing ten residues from the C-terminal of Cel5A, was expressed in a completely soluble form. tCel5A1 showed 7.3- fold increased specific activity against carboxy methyl cellulose while the increase in activities against regenerated amorphous cellulose and Avicel were 21 and 16 fold, respectively. tCel5A1 is stable at 60 °C for more than 2 hr and it showed temperature and pH optima 70 °C and 6.0, respectively, under the assay conditions used. These characteristics are similar to those of the native enzyme. As expected, CD spectral analysis showed that C-terminal truncation has little effect on the secondary structure of the molecule. tCel5A1 showed higher binding to pretreated rice straw (84%) as compared to the native form (46%). Molecular modelling analysis of tCel5A1 showed that the removal of C-terminal residues exposed the active site residues Glu253, Trp286, and Phe292, which are located in the catalytic cavity close to the C-terminus. Making these residues more accessible to the substrate would result in increased activity. The ratio of 10.01 between the soluble to the insoluble reducing groups produced from RAC on treatment with tCel5A1, and the presence of cellobiose as the major end product in the hydrolysate showed that tCel5A1 is a processive cellulase. Although other processive cellulases belonging to the family GH5, mainly of the fungal origin, have been reported, but tCel5A1, to our knowledge, is the first processive cellulase from an extreme thermophile reported so far.

cA novel thermoacidophilic pullulan-hydrolyzing enzyme (PUL) from hyperthermophilic archaeon Thermococcus kodakarensis (TK-PUL) that efficiently hydrolyzes starch under industrial conditions in the absence of any additional metal ions was cloned and characterized. TK-PUL possessed both pullulanase and ␣-amylase activities. The highest activities were observed at 95 to 100°C. Although the enzyme was active over a broad pH range (3.0 to 8.5), the pH optima for both activities were 3.5 in acetate buffer and 4.2 in citrate buffer. TK-PUL was stable for several hours at 90°C. Its half-life at 100°C was 45 min when incubated either at pH 6.5 or 8.5. The K m value toward pullulan was 2 mg ml ؊1 , with a V max of 109 U mg ؊1 . Metal ions were not required for the activity and stability of recombinant TK-PUL. The enzyme was able to hydrolyze both ␣-1,6 and ␣-1,4 glycosidic linkages in pullulan. The most preferred substrate, after pullulan, was ␥-cyclodextrin, which is a novel feature for this type of enzyme. Additionally, the enzyme hydrolyzed a variety of polysaccharides, including starch, glycogen, dextrin, amylose, amylopectin, and cyclodextrins (␣, ␤, and ␥), mainly into maltose. A unique feature of TK-PUL was the ability to hydrolyze maltotriose into maltose and glucose.