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6.
Chembiochem ; 19(17): 1873-1886, 2018 09 04.
Artículo en Inglés | MEDLINE | ID: mdl-29911308

RESUMEN

The acyclic molecule squalene (1) is cyclized into 6,6,6,6,5-fused pentacyclic hopene (2) and hopanol (3; ca. 5:1) through the action of Alicyclobacillus acidocaldarius squalene-hopene cyclase (AaSHC). The polycyclization reaction proceeds with regio- and stereochemical specificity under precise enzymatic control. This pentacyclic hopane skeleton is generated by folding 1 into an all-chair conformation. The Ala306 residue in AaSHC is conserved in known squalene-hopene cyclases (SHCs); however, increasing the steric bulk (A306T and A306V) led to the accumulation of 6,6,6,5-fused tetracyclic scaffolds possessing 20R stereochemistry in high yield (94 % for A306V). The production of the 20R configuration indicated that 1 had been folded in a chair-chair-chair-boat conformation; in contrast, the normal chair-chair-chair-chair conformation affords the tetracycle with 20S stereochemistry, but the yield produced by the A306V mutant was very low (6 %). Consequently, bulk at position 306 significantly affects the stereochemical fate during the polycyclization reaction. The SHC also accepts (3R) and (3S)-2,3-oxidosqualenes (OXSQs) to generate 3α,ß-hydroxyhopenes and 3α,ß-hydroxyhopanols through polycyclization initiated at the epoxide ring. However, the Val and Thr mutants generated epoxydammarane scaffolds from (3R)-OXSQ; this indicated that the polycyclization cascade started in these instances at the terminal double bond position. This work is the first to report the polycyclization of oxidosqualene starting at the terminal double bond.


Asunto(s)
Alicyclobacillus/enzimología , Transferasas Intramoleculares/química , Escualeno/análogos & derivados , Triterpenos/síntesis química , Alanina/química , Ciclización , Transferasas Intramoleculares/genética , Modelos Químicos , Mutagénesis Sitio-Dirigida , Escualeno/química , Estereoisomerismo
7.
J Hazard Mater ; 262: 25-30, 2013 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-24007995

RESUMEN

Diphenylarsinic acid (DPAA) is a toxic phenylarsenical compound often found around sites contaminated with phenylarsenic chemical warfare agents, diphenylcyanoarsine or diphenylchloroarsine, which were buried in soil after the World Wars. This research concerns the elucidation of the chemical structure of an arsenic metabolite transformed from DPAA under anaerobic sulfate-reducing soil conditions. In LC/ICP-MS analysis, the retention time of the metabolite was identical to that of a major phenylarsenical compound synthesized by chemical reaction of DPAA and hydrogen sulfide. Moreover the mass spectra for the two compounds measured using LC/TOF-MS were similar. Subsequent high resolution mass spectral analysis indicated that two major ions at m/z 261 and 279, observed on both mass spectra, were attributable to C12H10AsS and C12H12AsSO, respectively. These findings strongly suggest that the latter ion is the molecular-related ion ([M+H](+)) of diphenylthioarsinic acid (DPTA; (C6H5)2AsS(OH)) and the former ion is its dehydrated fragment. Thus, our results reveal that DPAA can be transformed to DPTA, as a major metabolite, under sulfate-reducing soil conditions. Moreover, formation of diphenyldithioarsinic acid and subsequent dimerization were predicted by the chemical reaction analysis of DPAA with hydrogen sulfide. This is the first report to elucidate the occurrence of DPAA-thionation in an anaerobic soil.


Asunto(s)
Arsenicales/química , Arsenicales/síntesis química , Contaminantes del Suelo/química , Sulfatos/química , Anaerobiosis , Cromatografía Líquida de Alta Presión , Espectrometría de Masa por Ionización de Electrospray
8.
J Am Chem Soc ; 133(44): 17540-3, 2011 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-21981578

RESUMEN

This study demonstrates that a tetraprenyl-ß-curcumene cyclase, which was originally identified as a sesquarterpene cyclase that converts a head-to-tail type of monocycle to a pentacycle, also cyclizes a tail-to-tail type of linear squalene into a bicyclic triterpenol, 8α-hydroxypolypoda-13,17,21-triene. The 8α-hydroxypolypoda-13,17,21-triene was found to be a natural triterpene from B. megaterium. It was also demonstrated that cyclizations of both tetraprenyl-ß-curcumene and squalene occurred with a purified B. megaterium TC homologue in the same reaction mixture. These results suggest that the tetraprenyl-ß-curcumene cyclase is bifunctional, cyclizing both tetraprenyl-ß-curcumene and squalene in vivo. This is the first report describing a bifunctional terpene cyclase, which biosynthesizes two classes of cyclic terpenes with different numbers of carbons as natural products in the organism.


Asunto(s)
Bacillus megaterium/enzimología , Liasas de Carbono-Oxígeno/metabolismo , Terpenos/metabolismo , Ciclización , Estructura Molecular , Estereoisomerismo , Terpenos/química
9.
J Am Chem Soc ; 133(25): 9734-7, 2011 Jun 29.
Artículo en Inglés | MEDLINE | ID: mdl-21627333

RESUMEN

In this study, mono- and pentacyclic C(35) terpenes from Bacillus subtilis were biosynthesized via the cyclization of C(35) isoprenoid using purified enzymes, including the first identified new terpene cyclase that shows no sequence homology to any of the known terpene cyclases. On the basis of these findings, we propose that these C(35) terpenes should be called the new family of "sesquarterpenes."


Asunto(s)
Bacillus subtilis/enzimología , Enzimas/metabolismo , Terpenos , Bacillus subtilis/metabolismo , Curcumina/análogos & derivados , Ciclización , Terpenos/metabolismo
11.
Artículo en Inglés | MEDLINE | ID: mdl-12921908

RESUMEN

The purpose of the present study was to determine the characteristics of repeatedly secluded female inpatients. Fifty female inpatients in a typical mental hospital were retrospectively investigated from the viewpoint of their recent history of seclusion, age, psychiatric symptoms rated by the Positive and Negative Syndrome Scale, doses of antipsychotics, and serum prolactin levels. The patients were divided into three groups (none, once, twice or more) by the frequency of seclusion in the most recent year. The three groups were significantly different in terms of positive symptoms, general psychopathological symptoms and serum prolactin levels. Unexpectedly, the seclusion frequency was negatively associated with serum prolactin levels. The present findings suggest that repeatedly secluded female inpatients suffered from relatively low prolactin levels as well as more positive and psychopathological symptoms. Further prospective studies are warranted to confirm these findings and to investigate whether low prolactin levels are useful in predicting the risk of frequent seclusion in female inpatients.


Asunto(s)
Pacientes Internos/psicología , Pacientes Internos/estadística & datos numéricos , Esquizofrenia/sangre , Aislamiento Social/psicología , Anciano , Análisis de Varianza , Femenino , Humanos , Persona de Mediana Edad , Prolactina/sangre , Estudios Retrospectivos
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