Linoleic acid isomerase was identified as a multi-component enzyme system that consists of three enzymes that exist in both the membrane and soluble fractions of Lactobacillus plantarum. One enzyme (CLA-HY) is present in the membrane fraction, while two enzymes (CLA-DH and CLA-DC) exist in the soluble fraction. Three Escherichia coli transformants expressing CLA-HY, CLA-DH, and CLA-DC were constructed. Conjugated linoleic acid (CLA) and 10-hydroxy-12-octadecenoic acid were generated from linoleic acid only when all these three E. coli transformants were used as catalysts simultaneously. CLA-HY catalyzed the hydration reaction, a part of linoleic acid isomerization, to produce 10-hydroxy-12-octadecenoic acid. This multi-component enzyme system required oxidoreduction cofactors such as NADH and FAD. This is the first report to reveal enzymes genes and the elaborate machinery that synthesizes CLA, especially an important isomer of cis-9, trans-11-CLA, in lactic acid bacteria.

Nitric oxide mediates vascular relaxing effects of endothelial cells, cytotoxic actions of macrophages and neutrophils, and influences of excitatory amino acids on cerebellar cyclic GMP. Its enzymatic formation from arginine by a soluble enzyme associated with stoichiometric production of citrulline requires NADPH and Ca2+. We show that nitric oxide synthetase activity requires calmodulin. Utilizing a 2',5'-ADP affinity column eluted with NADPH, we have purified nitric oxide synthetase 6000-fold to homogeneity from rat cerebellum. The purified enzyme migrates as a single 150-kDa band on SDS/PAGE, and the native enzyme appears to be a monomer.

Phylogenetic analysis has shown that Escherichia coli is composed of four main phylogenetic groups (A, B1, B2, and D) and that virulent extra-intestinal strains mainly belong to groups B2 and D. Actually, phylogenetic groups can be determined by multilocus enzyme electrophoresis or ribotyping, both of which are complex, time-consuming techniques. We describe a simple and rapid phylogenetic grouping technique based on triplex PCR. The method, which uses a combination of two genes (chuA and yjaA) and an anonymous DNA fragment, was tested with 230 strains and showed excellent correlation with reference methods.

Genetic diversity and relationships among 108 isolates of the bacterium Streptococcus pyogenes recently recovered from patients in the United States with toxic-shock-like syndrome or other invasive diseases were estimated by multilocus enzyme electrophoresis. Thirty-three electrophoretic types (ETs), representing distinctive multilocus clonal genotypes, were identified, but nearly half the disease episodes, including more than two-thirds of the cases of toxic-shock-like syndrome, were caused by strains of two related clones (ET 1 and ET 2). These two clones were also represented by recent pathogenic European isolates. A previous report of a relatively high frequency of expression of exotoxin A among isolates recovered from toxic-shock-like syndrome patients in the United States was confirmed; and the demonstration of this association both within clones and among distantly related clones supports the hypothesis that exotoxin A is a causal factor in pathogenesis of this disease. Near identity of the nucleotide sequences of the exotoxin A structural gene of six isolates of five ETs in diverse phylogenetic lineages was interpreted as evidence that the gene has been horizontally distributed among clones, presumably by bacteriophage-mediated transfer.

14-3-3-interacting proteins were isolated from extracts of proliferating HeLa cells using 14-3-3 affinity chromatography, eluting with a phosphopeptide that competes with targets for 14-3-3 binding. The isolated proteins did not bind to 14-3-3 proteins (14-3-3s) after dephosphorylation with protein phosphatase 2A (PP2A), indicating that binding to 14-3-3s requires their phosphorylation. The binding proteins identified by tryptic mass fingerprinting and Western blotting include many enzymes involved in generating precursors such as purines (AMP, GMP and ATP), FAD, NADPH, cysteine and S-adenosylmethionine, which are needed for cell growth, regulators of cell proliferation, including enzymes of DNA replication, proteins of anti-oxidative metabolism, regulators of actin dynamics and cellular trafficking, and proteins whose deregulation has been implicated in cancers, diabetes, Parkinsonism and other neurological diseases. Several proteins bound to 14-3-3-Sepharose in extracts of proliferating cells, but not in non-proliferating, serum-starved cells, including a novel microtubule-interacting protein ELP95 (EMAP-like protein of 95 kDa) and a small HVA22/Yop1p-related protein. In contrast, the interactions of 14-3-3s with the N-methyl-D-aspartate receptor 2A subunit and NuMA (nuclear mitotic apparatus protein) were not regulated by serum. Overall, our findings suggest that 14-3-3s may be central to integrating the regulation of biosynthetic metabolism, cell proliferation, survival, and other processes in human cells.

We report a general mass spectrometric approach for the rapid identification and characterization of proteins isolated by preparative two-dimensional polyacrylamide gel electrophoresis. This method possesses the inherent power to detect and structurally characterize covalent modifications. Absolute sensitivities of matrix-assisted laser desorption ionization and high-energy collision-induced dissociation tandem mass spectrometry are exploited to determine the mass and sequence of subpicomole sample quantities of tryptic peptides. These data permit mass matching and sequence homology searching of computerized peptide mass and protein sequence data bases for known proteins and design of oligonucleotide probes for cloning unknown proteins. We have identified 11 proteins in lysates of human A375 melanoma cells, including: alpha-enolase, cytokeratin, stathmin, protein disulfide isomerase, tropomyosin, Cu/Zn superoxide dismutase, nucleoside diphosphate kinase A, galaptin, and triosephosphate isomerase. We have characterized several posttranslational modifications and chemical modifications that may result from electrophoresis or subsequent sample processing steps. Detection of comigrating and covalently modified proteins illustrates the necessity of peptide sequencing and the advantages of tandem mass spectrometry to reliably and unambiguously establish the identity of each protein. This technology paves the way for studies of cell-type dependent gene expression and studies of large suites of cellular proteins with unprecedented speed and rigor to provide information complementary to the ongoing Human Genome Project.

Bacteriophage lytic enzymes quickly destroy the cell wall of the host bacterium to release progeny phage. Because such lytic enzymes specifically kill the species in which they were produced, they may represent an effective way to control pathogenic bacteria without disturbing normal microflora. In this report, we studied a murein hydrolase from the streptococcal bacteriophage C(1) termed lysin. This enzyme is specific for groups A, C, and E streptococci, with little or no activity toward several oral streptococci or other commensal organisms tested. Using purified lysin in vitro, we show that 1,000 units (10 ng) of enzyme is sufficient to sterilize a culture of approximately 10(7) group A streptococci within 5 seconds. When a single dose of lysin (250 units) is first added to the oral cavity of mice, followed by 10(7) live group A streptococci, it provides protection from colonization (28.5% infected, n = 21) compared with controls without lysin (70.5% infected, n = 17)(P < 0.03). Furthermore, when lysin (500 units) was given orally to 9 heavily colonized mice, no detectable streptococci were observed 2 h after lysin treatment. In all, these studies show that lysin represents a unique murein hydrolase that has a rapid lethal effect both in vitro and in vivo on group A streptococci, without affecting other indigenous microorganisms analyzed. This general approach may be used to either eliminate or reduce streptococci from the upper respiratory mucosal epithelium of either carriers or infected individuals, thus reducing associated disease.