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An attempt has been made for enhancing the thermostability of xylanase (Mxyl) retrieved from a compost-soil-based metagenomic library. The analysis of the structure of xylanase by molecular dynamics simulation revealed more structural fluctuations in β-sheets. When the surface of β-sheets was enriched with arginine residues by substituting serine/threonine by site-directed mutagenesis, the enzyme with four arginine substitutions (MxylM4) exhibited enhanced thermostability at 80 °C. The T 1/2 of MxylM4 at 80 °C, in the presence of birchwood xylan, increased from 130 to 150 min at 80 °C without any alteration in optimum pH and temperature and molecular mass. Improvement in thermostability of MxylM4 was corroborated by increase in T m by 6 °C over that of Mxyl. The K m of MxylM4, however, increased from 8.01 ± 0.56 of Mxyl to 12.5 ± 0.32 mg ml−1, suggesting a decrease in the affinity as well as specific enzyme activity. The Mxyl as well as MxylM4 liberated chromophores and lignin-derived compounds from kraft pulp, indicating their applicability in pulp bleaching.

NG, N G - Dimethylarginine ( unsym - DMA ) has now been found to be present in myosin prepared from developing leg muscle. Neither monomethylarginine nor sym - DMA (NG N ′ G - dimethylarginine ) could be detected in our preparations. Cultured muscle cell myosin contains up to four residues of this amino acid per 5 × 105 grams of protein. Myosins from leg muscle of chick embryos and neonatal rats contained less than two residues of unsym - DMA , while none was detected in adult chicken or rat myosins. Cardiac myosins from developing as well as mature animals lacked or contained very little unsym - DMA . Actin was devoid of this amino acid.

Alkaline solutions of amino acids absorb carbon dioxide, giving carbamates, which may appear as additional spots or streaks after paper electrophoresis in alkaline electrolytes. Interference from carbamates is prevented by carrying out electrophoresis at 50°. Mixtures of arginine, histidine, citrulline, ornithine, and lysine are resolved by paper electrophoresis at 50° and pH 9.2 in an electrolyte containing sodium carbonate and sodium hydrogen carbonate. Addition of 8-hydroxyquinoline prevents interference from impurities in the paper.

The active thiol group of lombricine kinase from Lumbricus terrestris muscle was labelled with N-ethyl-[1-14C]maleimide. The resulting inactivated N-ethyl-[1-14C]succinimido enzyme was then subjected to tryptic hydrolysis. The peptide containing the labelled essential thiol group was isolated and found to contain: Leu-Gly-Tyr-Ile-Thr-[14C]Cys-Pro-Gly-Ser-Asn-Leu-Gly-Thr-Leu-Arg. The amino acid sequence around this thiol group was very similar with that of homologous ATP: guanidine phosphotransferases previously studied, arginine kinase from Homarus vulgaris muscle, creatine kinases from ox brain and ox muscle and from rabbit muscle. In addition among the other enzymes of this group, lombricine kinase is of special interest since it is the only dimeric enzyme of molecular weight ≃ 80000 which possesses only one essential thiol group and one nucleotide binding site per two subunits.

Unfractionated bromegrass mosaic virus RNA and each of its three naturally occurring components, of molecular weight 1.0 × 10 6 , 0.7 × 10 6 , and 0.3 × 10 6 , stimulate the incorporation of amino acids into peptides in an E. coli cell-free incorporating system. Analysis of tryptic digests by paper electrophoresis and chromatography indicated that the products induced by the RNA small component of molecular weight 0.3 × 10 6 , and by the unfractionated RNA were similar.

The cationic antibacterial proteins of rabbit PMN lysosomes have been resolved into at least five subfractions. Each of these showed substantial selectivity in its antibacterial action against several pathogenic bacteria, including two smooth and two rough Escherichia coli strains, three Staphylococcus aureus strains, one S. albus, three proteus species and four different cultures of streptococcus. Each of the subfractions possesses a different electrophoretic mobility. Amino acid analyses of the three most cationic components revealed high contents of arginine consistent with their relative electrophoretic mobilities and very high arginine to lysine ratios. Aromatic amino acids were present in very low concentrations in these proteins and their light absorption at 2800 A was correspondingly weak. The evidence of antibacterial specificity, along with marked differences in the arginine-lysine ratios, shows that the cationic antibacterial components of rabbit PMN lysosomes are biologically and chemically heterogeneous.

It is shown that either or both of two α-lactalbumins (designated A and B) may occur in the milk of Droughtmaster cattle. Their occurrence is genetically determined. The B variant has the same amino acid composition as the sole α-lactalbumin occurring in the milk of European breeds and the A variant differs from the B variant having one less arginine residue (0 vs. 1) and one more glutamine residue. There are two peptides in the map of the B variant that are not present in the map of A, and one peptide in B not present in A. These difference peptides have been isolated and their amino acid composition and electrophoretic mobility determined. One peptide has been subjected to Edman degradation. The data are considered in the light of the known partial sequence of α-lactalbumin of European breeds. It is concluded tentatively that the substitution of glutamine in A for arginine in B occurs at residue No. 10.