Synthesis of allysine ethylene acetal using phenylalanine dehydrogenase from Thermoactinomyces intermedius

Allysine ethylene acetal [(S)-2-amino-5-(1,3-dioxolan-2-yl)-pentanoic acid (2)] was prepared from the corresponding keto acid by reductive amination using phenylalanine dehydrogenase (PDH) from Thermoactinomyces intermedius ATCC 33205. Glutamate, alanine, and leucine dehydrogenases, and PDH from Sporosarcina species (listed in order of increasing effectiveness) also gave the desired amino acid but were less effective. The reaction requires ammonia and NADH. NAD produced during the reaction was recyled to NADH by the oxidation of formate to CO(2) using formate dehydrogenase (FDH). PDH was produced by growth of T. intermedius ATCC 33205 or by growth of recombinant Escherichia coli or Pichia pastoris expressing the Thermoactinomyces enzyme. Using heat-dried T. intermedius as a source of PDH and heat-dried Candida boidinii SC13822 as a source of FDH,98%, but production of T. intermedius could not be scaled up. Using heat-dried recombinant E. coli as a source of PDH and heat-dried Candida boidinii 98%. In a third generation process, heat-dried methanol-grown P. pastoris expressing endogenous FDH and recombinant Thermoactinomyces98% ee.     

Basal cell adenocarcinoma of the salivary gland: report of a case with morphology on fine needle aspiration cytology

BACKGROUND: Basal cell adenocarcinoma of the parotid is rare and prone to recur. CASE: A 54-year-old woman had a history of afacial mass 12 years earlier that had been excised and was diagnosed as low grade adenocarcinoma of the parotid. Over the years, the patient had multiple local and lymph node recurrences. Histology of the excised local recurrent tumor showed basal cell adenocarcinoma, and FNAC of a separate recurrent nodule was performed. The aspirate showed moderate cellularity of basaloid cells with mildly pleomorphic nuclei, small nucleoli and occasional mitotic figures. The cells were mostly single, but some formed clusters with a rosettelike pattern of tumor cells surrounding central eosinophilic globules. A second, less prominent population of smaller cells with dark-staining nuclei was also noted. The differential diagnosis included adenoid cystic carcinoma, polymorphous low grade adenocarcinoma, and basal cell and pleomorphic adenoma. CONCLUSION: The cytologic features of basal cell adenocarcinoma are not distinctive, but the presence of two cell populations with moderate pleomorphism and a rosettelike pattern with central, eosinophilic globules may assist with its differentiation from other salivary gland neoplasms.     

Characterization of nucleoside transport systems in cultured rat epididymal epithelium

The nucleoside transport systems in cultured epididymal epithelium were characterized and found to be similar between the proximal (caput and corpus) and distal (cauda) regions of the epididymis. Functional studies revealed that 70% of the total nucleoside uptake was Na(+) dependent, while 30% was Na(+) independent. The Na(+)-independent nucleoside transport was mediated by both the equilibrative nitrobenzylthioinosine (NBMPR)-sensitive system (40%) and the NBMPR-insensitive system (60%), which was supported by a biphasic dose response to NBMPR inhibition. The Na(+)-dependent [(3)H]uridine uptake was selectively inhibited 80% by purine nucleosides, indicating that the purine nucleoside-selective N1 system is predominant. Since Na(+)-dependent [(3)H]guanosine uptake was inhibited by thymidine by 20% and Na(+)-dependent [(3)H]thymidine uptake was broadly inhibited by purine and pyrimidine nucleosides, this suggested the presence of the broadly selective N3 system accounting for 20% of Na(+)-dependent nucleoside uptake. Results of RT-PCR confirmed the presence of mRNA for equilibrative nucleoside transporter (ENT) 1, ENT2, and concentrative nucleoside transporter (CNT) 2 and the absence of CNT1. It is suggested that the nucleoside transporters in epididymis may be important for sperm maturation by regulating the extracellular concentration of adenosine in epididymal plasma.     

Further investigation on the turnover of Escherichia coli biotin synthase with dethiobiotin and 9-mercaptodethiobiotin as substrates

Biotin synthase, a member of the "radical-SAM" family, produces biotin by inserting a sulfur atom between C-6 and C-9 of dethiobiotin. Each of the two saturated carbon atoms is activated through homolytic cleavage of a C-H bond by a deoxyadenosyl radical, issued from the monoelectronic reduction of S-adenosylmethionine (SAM or AdoMet). An important unexplained observation is that the enzyme produces only 1 mol of biotin per enzyme monomer. Some possible reasons for this absence of multiple turnovers are considered here, in connection with the postulated mechanisms. There is a general agreement among several groups that the active form of biotin synthase contains one (4Fe-4S)(2+,1+) center, which mediates the electron transfer to AdoMet, and one (2Fe-2S)(2+) center, which is considered the sulfur source [Ugulava, N. B., Sacanell, C. J., and Jarrett, J. T. (2001) Biochemistry 40, 8352-8358; Tse Sum Bui, B., Benda, R., Schunemann, V., Florentin, D., Trautwein, A. X., and Marquet, A. (2003) Biochemistry 42, 8791-8798; Jameson, G. N. L., Cosper, M. M., Hernandez, H. L., Johnson, M. K., and Huynh, B. H. (2004) Biochemistry 43, 2022-2031]. An alternative hypothesis considers that biotin synthase has a pyridoxal phosphate (PLP)-dependent cysteine desulfurase activity, producing a persulfide which could be the sulfur donor. The absence of turnover was explained by the inhibition due to deoxyadenosine, an end product of the reaction [Ollagnier-de Choudens, S., Mulliez, E., and Fontecave, M. (2002) FEBS Lett. 535, 465-468]. In this work, we show that our purified enzyme has no cysteine desulfurase activity and the required sulfide has to be added as Na(2)S. It cannot be replaced by cysteine, and consistently, PLP has no effect. We observed that deoxyadenosine does not inhibit the reaction either. On the other hand, if the (2Fe-2S)(2+) center is the sulfur source, its depletion after reaction could explain the absence of turnover. We found that after addition of fresh cofactors, including Fe(2+) and S(2)(-), either to the assay when one turn is completed or after purification of the reacted enzyme by different techniques, only a small amount of biotin (0.3-0.4 equiv/monomer) is further produced. This proves that an active enzyme cannot be fully reconstituted after one turn. When 9-mercaptodethiobiotin, which already contains the sulfur atom of biotin, is used as the substrate, the same turnover of one is observed, with similar reaction rates. We postulate that the same intermediate involving the (2Fe-2S) cluster is formed from both substrates, with a rate-determining step following the formation of this intermediate.     

Cytotoxic activities of Coriolus versicolor (Yunzhi) extract on human leukemia and lymphoma cells by induction of apoptosis

Coriolus versicolor (CV), also known as Yunzhi, is one of the commonly used Chinese medicinal herbs. Although recent studies have demonstrated its antitumour activities on cancer cells in vitro and in vivo, the exact mechanism is not fully elucidated. Hence, the objective of this study was to examine the in vitro cytotoxic activities of a standardized aqueous ethanol extract prepared from Coriolus versicolor on a B-cell lymphoma (Raji) and two human promyelocytic leukemia (HL-60, NB-4) cell lines using a MTT cytotoxicity assay, and to test whether the mechanism involves induction of apoptosis. Cell death ELISA was employed to quantify the nucleosome production resulting from nuclear DNA fragmentation during apoptosis. The present results demonstrated that CV extract at 50 to 800 microg/ml dose-dependently suppressed the proliferation of Raji, NB-4, and HL-60 cells by more than 90% (p < 0.01), with ascending order of IC50 values: HL-60 (147.3 +/- 15.2 microg/ml), Raji (253.8 +/- 60.7 microg/ml) and NB-4 (269.3 +/- 12.4 microg/ml). The extract however did not exert any significant cytotoxic effect on normal liver cell line WRL (IC50 > 800 microg/ml) when compared with a chemotherapeutic anticancer drug, mitomycin C (MMC), confirming the tumour-selective cytotoxicity. Nucleosome productions in HL-60, NB-4 and Raji cells were significantly increased by 3.6-, 3.6- and 5.6-fold respectively upon the treatment of CV extract, while no significant nucleosome production was detected in extract-treated WRL cells. The CV extract was found to selectively and dose-dependently inhibit the proliferation of lymphoma and leukemic cells possibly via an apoptosis-dependent pathway.     

Comparison of anti-hyperglycemic effect amongst vanadium, molybdenum and other metal maltol complexes

A wide variety of vanadium-containing complexes have been tested, both in vivo and in vitro, as possible therapeutic agents for the oral treatment of type 2 diabetes mellitus. None so far has surpassed bis(maltolato)oxovanadium(IV) (BMOV) for glucose- and lipid-lowering in an orally available formulation. Ligand choice is clearly an important factor in pharmacological efficacy of vanadium compounds as insulin enhancing agents. In this study, we kept the ligand and dose the same, varying instead the metal ion bound to the maltolato ligand in a series of binary complexes of neutral charge. A requirement for vanadyl ion as the metal ion of choice was apparent; no other metal ion tested served as a suitable substitute. Amongst [MoO(2)](2+), Co(II), Cu(II), Cr(III), and Zn(II), only [MoO(2)](2+) and Co(II) showed any hypoglycemic activity at the ED(50) dose for bis(maltolato)oxovanadium(IV), 0.6 mmolkg(-1) by oral gavage in streptozotocin (STZ)-diabetic rats within 72 h of administration of compound.