Enzyme-like Regiodivergent Behavior of a Flavopeptide Catalyst in Aerobic Baeyer-Villiger Oxidation

We recently developed a flavopeptide immobilized on polystyrene resin, Fl-Pep-PS, that could realize the first N5-unmodified neutral flavin (Fl)-catalyzed aerobic oxygenation reactions under non-enzymatic conditions. Although a key active species is assumed to be the corresponding 4a-hydroperoxyflavin (Fl4aOOH) from the unprecedented activity and unique chemoselectivity, further circumstantial support would be helpful to be sure since spectroscopic evidence is difficult to obtain due to the compound’s insolubility. In this article, we report that the aerobic Baeyer-Villiger oxidation of a fused cyclobutanone, (±)-cis-bicyclo[3.2.0]hept-2-en-6-one (1), can be promoted with Fl-Pep-PS in a FMO-like chemoselectivity and regiodivergent manner via Fl-related catalytic intermediates, which delivers strong evidence of the involvement of Fl4aOOH as an active species in Fl-Pep-PS-catalyzed aerobic oxygenation reactions

Design of peptide-containing N5-unmodified neutral flavins that catalyze aerobic oxygenations

Simulation of the monooxygenation function of flavoenzyme (Fl-Enz) has been long-studied with N5-modified cationic flavins (FlEt+), but never with N5-unmodified neutral flavins (Fl) despite the fact that Fl is genuinely equal to the active center of Fl-Enz. This is because of the greater lability of 4a-hydroperoxy adduct of Fl, FlOOH, compared to those of FlEt+, FlEtOOH, and Fl-Enz, FlOOH-Enz. In this study, Fl incorporated into a short peptide, flavopeptide (Fl-Pep), was designed by a rational top-down approach using a computational method, which could stabilize the corresponding 4a-hydroperoxy adduct (FlOOH-Pep) through intramolecular hydrogen bonds. We report catalytic chemoselective sulfoxidation as well as Baeyer–Villiger oxidation by means of Fl-Pep under light-shielding and aerobic conditions, which are the first Fl-Enz-mimetic aerobic oxygenation reactions catalyzed by Fl under non-enzymatic conditions

The Genetic Diversity of Helicobacter pylori Virulence Genes Is Not Associated with Gastric Atrophy Progression

Atrophy of the gastric mucosa is a precursor of intestinal-type gastric cancer, and Helicobacter pylori infection causes atrophic gastritis. The aim of this study was to determine whether the genetic diversity of H. pylori virulence genes is associated with the development and progression of gastric atrophy in humans. We isolated and cultured H. pylori strains from patients with gastric ulcer and duodenal ulcer accompanied by atrophic gastritis in background mucosa. H. pylori strains were stored at －80℃ prior to the experiments being carried out. We analyzed iceA, babA, vacA, cagA, and cagE genes by PCR. The cagA gene was analyzed through sequencing of the C-terminal region containing the EPIYA motif, which is related to tyrosine phosphorylation. Severe atrophy was observed in patients with gastric ulcer. The major phenotype of the vacA gene was s1c/m1 (93ｵ). The cagA gene was detected in all strains. The cagE gene was not detected in 2 and 5 strains from the mild cases and severe cases, respectively. The major cagA EPIYA motif, which is amino acids repeat in the C terminus, was the A-B-D type (44 of 58 strains). The virulence genes were not statistically associated with the severity of atrophy in the background gastric mucosa in humans. Not only identification of bacterial virulence factors but also studies of the host response will be necessary to investigate the progression of gastric atrophy and subsequent cancer development in humans

Immune Reactions Against Elongation Factor 2 Kinase: Specific Pathogenesis of Gastric Ulcer from Helicobacter pylori Infection

Helicobacter pylori (H. pylori) infection is a definite causative factor for gastric ulcers (GUs). In the present study we detected a specific antigen of gastric epithelial cells (HGC-27) using cell ELISA, which was recognized by the sera of GU patients (n = 20) but not in patients with chronic gastritis (CG; n = 20) or in healthy volunteers (HC; n = 10). This antigen was over-expressed by a stressful (heat-stressed) environment, and was identified as elongation factor 2 kinase (EF-2K) by western blotting. The GU patients' lymphocytes stimulated by H. pylori specifically disrupted heat-stressed HGC-27 cells in a cytotoxic assay. In flow cytometry, the effector cells (lymphocytes) from GU patients were significantly differentiated to T helper type 1 lymphocyte (Th1) and cytotoxic T lymphocyte (CTL) as opposed to those from CG patients. The target cells (HGC-27) expressed EF-2K and MHC-class I together with costimulatory molecules from heat stress. This antigen specific immune mechanism could have a prominent role in the pathogenesis of GU

Comparison of estimation methods of liver maximum removal rate of indocyanine green.

Three linear plots by which the liver's maximum removal rate (Rmax) of indocyanine green (ICG) and the Michaelis constant (Km) can be calculated were compared in a microcomputer simulation study. The widely-used Lineweaver-Burk plot (1/V vs. 1/S; V, ICG initial removal rate (mg/kg/min); S, ICG loading dose (mg/kg] presented the greatest bias and variance. There was no remarkable difference in bias between the S/V vs. S plot and the V vs. V/S plot, but the latter possessed a smaller variance. Therefore, the V vs. V/S plot was considered the best for estimating Rmax. The best combination of three ICG loading doses was 0.5, 2, and 5 mg/kg. This combination was selected by comparison of the Rmax estimated from three points with that estimated from six points (0.5, 1, 2, 3, 4 and 5 mg/kg).</p

Scanning electron microscopy of Ito's fat-storing cells in the rat liver.

The whole body including extended processes of Ito's fat-storing cells was observed by scanning electron microscopy in rat liver injured with lithocholic acid (LCA). Necrotic foci developed in the midlobular zone 48 h after LCA administration. Demonstration of Ito cell bodies around the foci was probably facilitated by easy detachment of hepatocytes from Ito cells. The body and the processes were located mainly between the sinusoidal endothelium and hepatocytes; sometimes they were between hepatocytes. Ito cells often were proximate to collagen fiber bundles and sometimes were attached to them. The cell body was flatly round or elliptic, 7 to 12 micron in diameter. Its surface was finely undulated with microvillous projections about 0.1 micron in length. Branching patterns of the processes resembled a fern-leaf mantling the sinusoidal endothelium. The trunks of the processes were about 2 micron in diameter and 20-30 micron in length. These processes tapered, branching into thinner processes, with the most peripheral being 0.1 micron in diameter. Ito cells and their branching processes likely strengthen sinusoidal walls and control blood flow in the sinusoids.</p

Computed tomographic arteriography in the diagnosis of hepatocellular carcinoma.

Computed tomographic arteriography (CTA) was performed in 30 patients with hepatocellular carcinoma (HCC). Detection of HCC by CTA was compared with that of conventional celiac or hepatic arteriography. CT scanning was performed immediately, 30 seconds and 1 min after an injection of 5 to 10 ml of contrast medium into the common or proper hepatic artery. Repeated infusions allowed whole liver sections to be visualized. HCC was localized in 28 of the 30 patients by conventional arteriography, with CTA detecting the masses in 27 of the 28 patients. CTA imaging presented the tumor mass in 1 of the 2 patients missed by arteriography. Conventional arteriography delineated the boundaries of HCC in 15 (50%) of the 30 patients. CTA clearly delineated the masses in 26 (87%) of the 30 patients including 11 patients in which the tumor borders were obscure by conventional arteriography. HCC lesions smaller than 1 cm in diameter were detected only by CTA in 6 (20%) of the patients. It was concluded that CTA is both useful and necessary in the demarcation of small HCC masses.</p

Peritoneoscopy of alcoholic liver cirrhosis in comparison with non-alcoholic liver cirrhosis.

Peritoneoscopic findings of 39 patients with alcoholic liver cirrhosis (ALC) were compared with those of 95 patients with non-alcoholic liver cirrhosis (NALC). They were selected from 245 patients with liver cirrhosis subjected to peritoneoscopy in the 7 year period from 1975 to 1981. Out of the 95 NALC patients, 24 had hepatitis B surface antigen. The ALC patients had nodules which varied in size (61%), large depressions (69%), and a markedly rounded edge of the liver (33%) more often than NALC patients (18, 43 and 3%, respectively). Nodularity differed between the right and left lobes in ALC (41%) more often than in NALC (16%). Interstitial reddish markings and patchy nodules were, however, more frequent in NALC (51 and 28%, respectively) than in ALC (8 and 5%, respectively). Lymphatic vesicles were observed both in ALC (85%) and NALC (78%). In conclusion, the peritoneoscopic features which suggested ALC were the coexistence of nodules of various sizes, large depressions and a markedly dull edge of the liver. Interstitial reddish markings and patchy nodules were more indicative of NALC than ALC.</p

Effects of sake and bourbon on liver histopathology and function in rats.

Sake or bourbon (8g ethanol/kg body weight) was intragastrically administered to rats for 12 days. An equal dose of ethanol in water or an isocaloric glucose solution was administered to control groups. Food was withheld, but water freely provided. Neither mortality nor liver and body weights were different between the alcohol-treated groups. Glutamic oxaloacetic transaminase and glutamic pyruvic transaminase were more elevated in the sake group than in the other groups. Additionally, liver fibrosis was more pronounced, and vacuole formation or steatosis was less in this group. These results suggest that sake is more fibrogenic. Some components other than ethanol, such as long-alkyl chain alcohols, may have been responsible for the differential histopathology.</p

Comparative diagnosis of alcoholic liver diseases by multivariate and histological analysis.

Sixty-seven cases of alcoholic liver disease were histologically classified into 4 groups: alcoholic liver cirrhosis (ALC), alcoholic hepatitis (AH), alcoholic liver fibrosis (ALF) and alcoholic fatty liver (AFL). They were statistically reclassified by the likelihood method using age, total alcohol intake, hepatomegaly and 12 liver function tests. A score table for likely diagnosis was constructed from the incidences of each range. The cases were re-evaluated using the score table, with an overall correct diagnosis rate of 73%. The best combination of 5 parameters included the indocyanine green plasma disappearance rate, total alcohol intake, cholesterol, choline esterase and glutamic oxaloacetic transaminase/glutamic pyruvic transaminase ratio. A correct diagnosis rate of 75% was attained using these 5 parameters, and 94% of patients were correctly diagnosed by the first or the second likelihood diagnosis. Differential diagnosis of alcoholic liver diseases was easily and confidently obtained with the likelihood score table.</p