Natural,semisynthetic and synthetic tyrosinase inhibitors

Tyrosinase plays a pivotal role in the synthesis of melanin pigment synthesis on skin utilizing tyrosine as a substrate. Melanin is responsible for the protection against harmful ultraviolet irradiation, which can cause significant pathological conditions, such as skin cancers. However, it can also create esthetic problems when accumulated as hyperpigmented spots. Various skin-whitening ingredients which inhibit tyrosinase activity have been identified. Some of them, especially ones with natural product origins, possess phenolic moiety and have been employed in cosmetic products. Semi-synthetic and synthetic inhibitors have also been developed under inspiration of the natural inhibitors yet some of which have no phenolic groups. In this review, tyrosinase inhibitors with natural, semi-synthetic and synthetic origins are listed up with their structures, activities and characteristics. Further, a recent report on the adverse effect of a natural melanin synthesis inhibitor which was included in skin-whitening cosmetics is also briefly discussed.     

Secretion of Recombinant Pediocin PA-1 by Bifidobacterium longum, Using the Signal Sequence for Bifidobacterial α-Amylase

A recombinant DNA, encoding the chimeric protein of the signal sequence for bifidobacterial α-amylase mature pediocin PA-1, was introduced into Bifidobacterium longum MG1. Biologically active pediocin PA-1 was successfully secreted from the strain and showed bactericidal activity against Listeria monocytogenes and the same molecular mass as native pediocin PA-1.     

Cancer Cell Analyses at the Single Cell-Level Using Electroactive Microwell Array Device

Circulating tumor cells (CTCs), shed from primary tumors and disseminated into peripheral blood, are playing a major role in metastasis. Even after isolation of CTCs from blood, the target cells are mixed with a population of other cell types. Here, we propose a new method for analyses of cell mixture at the single-cell level using a microfluidic device that contains arrayed electroactive microwells. Dielectrophoretic (DEP) force, induced by the electrodes patterned on the bottom surface of the microwells, allows efficient trapping and stable positioning of single cells for high-throughput biochemical analyses. We demonstrated that various on-chip analyses including immunostaining, viability/apoptosis assay and fluorescent in situ hybridization (FISH) at the single-cell level could be conducted just by applying specific reagents for each assay. Our simple method should greatly help discrimination and analysis of rare cancer cells among a population of blood cells.     

Continuous culture of a recombinantEscherichia coli and plasmid maintenance for tryptophan production

Summary Production of tryptophan by a temperature sensitive recombinant microorganism (Escherichia coli W3110 trpLDtrpR ^ts tna ^– (pCRT185)) was investigated. In a single-stage continous culture, at an elevated temperature, 42°C (derepressed condition), tryptophan concentration increased in an early phase of the fermentation, and then gradually decreased with time. The reduction in the production rate was mostly due to the segregation of the plasmid and subsequent increase of plasmid-free cells. However, the plasmid could be maintained stable at 37°C, with repressed condition oftrp-operon, over 200 generations. A two-stage continuous culture system, i.e. cell growth was maintained in the first stage at 37°C and gene expression was induced in the second stage at 42°C, was therefore tested to improve the performance of the fermentation system. Operation of the two-stage system showed that the plasmid stability was significantly improved, and the specific rate of tryptophan production was maintained almost constant for more than 500 hours in the second stage.     

Elementary steps in the formation of horseradish peroxidase compound I: direct observation of compound 0, a new intermediate with a hyperporphyrin spectrum

The reaction of horseradish peroxidase (HRP) with H2O2 has been studied in 50% v/v methanol/water over the 25.0 to -36.0 degrees C temperature range by using the low-temperature stopped-flow technique. All reactions were carried out under pseudo-first-order conditions with [H2O2] much greater than [HRP]. Arrhenius plots for the pseudo-first-order rate constant kobs were linear over the 17.6 to -36.0 degrees C temperature range studied with an activation energy of 4.8 +/- 0.5 kcal/mol. Above 0 degrees C, kobs varies linearly with peroxide concentration. However, saturation kinetics are observed below -16.0 degrees C, indicating that there is at least one reversible elementary step in this reaction. Double-reciprocal plots at -26.0 degrees C at pH* 7.3 for the reaction give kappa max(obs) = 163 s-1 and KM = 0.190 mM. Rapid-scan optical studies carried out at -35.0 degrees C with [H2O2] much greater than KM reveal the presence of a transient intermediate referred to as compound 0 whose conversion to compound I is rate limiting. The Soret region of the optical spectrum of compound 0 resembles that of a "hyperporphyrin" with prominent bands near 330 and 410 nm. The temperature dependencies of kappa max(obs) and KM have been measured over the -16.0 to -26.0 degrees C range and give an activation energy for kappa max(obs) of 1.6 +/- 0.7 kcal/mol and an enthalpy of formation for compound 0 of 4.0 +/- 0.7 kcal/mol.     

Genotype of Yupik Eskimos with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Summary An A-to-G transition in the second intron was the sole mutation detected in four Yupik Eskimo patients with salt-wasting congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency. Allele-specific hybridization should be an efficient means of performing prenatal diagnosis of the disease in this highly inbred population.     

Pilot-scale production of l-phenylalanine from d-glucose

Effects of inoculum size and total sugar content on both l-phenylalanine productivity and titre have been investigated using a tyrosine auxotrophic regulatory mutant of Escherichia coli. Fermentations were carried out in a 500 litre pilot fermenter with intermittent feeding of d-glucose plus phosphate. It was found that the productivity was not greatly affected by inoculum size. However, the l-phenylalanine titre was significantly affected by total sugar content. Relatively high productivities of up to 0.35–0.40 g l-phenylalanine l^?1 h^?1 have been achieved at l-phenylalanine titres of 14–15 g l^?1.     

Digestion by the larva of the pruinose scarab, Sericesthis geminata

An in vitro study of digestion by the subterranean larva of S. geminata revealed the presence of enzymes able to digest starch, trehalose, salicin, cellobiose, melibiose, maltose, sucrose, casein, and several forms of cellulose. The midgut is the major source of all enzymes except invertase and CMC-cellulase, for which hindgut preparations are more active. The pH values of the gut contents are: foregut 6.9, midgut 9.0 and hindgut 7.5. The midgut fluid is pumped forward into the foregut, and the carbohydrases in it are generally more active at the pH of the foregut than at the pH of the midgut. It is possible, therefore, that the foregut, which is itself insignificant as a source of enzymes, is the site of considerable carbohydrate digestion. The proteinase is inhibited 28% by trypsin inhibitors.

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Zusammenfassung Eine in vitro-Untersuchung über die Verdauungsvorgänge in den unterirdisch lebenden Larven von S. geminata wies Enzyme nach, die Stärke, Trehalose, Salicin, Cellobiose, Melibiose, Maltose, Rohrzucker, Kasein und mehrere Celluloseformen abbauen können. Versuche mit Vorder-, Mittel- und Enddarmextrakten zeigten, daß der Abbau von Rohrzucker und CMC-Cellulose in Ansätzen mit Enddarmpräparaten prozentual am höchsten war. Maximale Verdauung aller anderen geprüften Substrate erfolgte dagegen mit Mitteldarmpräparaten.Die pH-Werte betrugen im Vorderdarm 6,9, im Mitteldarm 9,0 und im Enddarm 7,5. Im Mittel- und Enddarm lagen die jewciligen optimalen pH-Werte für Maltose bei 6,5–7,0 und 7,5, für Melibiose bei 6,0–7,0 und 7,0–7,5, für Cellobiose bei 6,0–7,0 und 4,5, für Rohrzucker bei 7,0 und 6,0, für CMC bei 5,2 und 5,6.Die Verdauung unlöslicher Celluloseformen war durchweg gering, die der CMC dagegen beträchtlich.Die Mitteldarmflüssigkeit wird nach vorn in den Vorderdarm gepumpt. Die darin enthaltenen Carbohydrasen sind beim pH-Wert des Vorderdarmes meistens wirksamer als in dem des Mitteldarmes. Es ist deshalb möglich, daß im Vorderdarm, welcher selbst wahrscheinlich keine Enzyme produziert, doch eine beträchtliche Kohlenhydratverdauung stattfindet.Die Wirksamkeit der Proteinase wird durch bekannte Tryptin-Hemmstoffe um 28% reduziert.