Polymyxin Acylase: An Enzyme Causing Intramolecular N2⇄N6 Acyl Transfer in N-Monooctanoyl-l-Lysine

Polymyxin acylase from Pseudomonas sp. M-6-3 can deacylate not only polymyxin antibiotics, but also A-fatty acyl-peptides and N-fatty acyl-amino acids. We found that this enzyme causes intramolecular N²?N⁶ acyl transfer in monooctanoyl-l-lysine; when N²-octanoyl-l-lysine is the substrate, N⁶-octanoyl- l-lysine is produced at pH 10.5, but when N⁶-octanoyl- l-lysine is the substrate, N²-octanoyl- l-lysine is produced at pH 8.0. In these reactions, the deacylation proceeded gradually at the final stage and eventually, both N²-octanoyl- l-lysine and N⁶-octanoyl- l-lysine were hydrolyzed to l-lysine and octanoic acid. Furthermore, this enzyme showed intermolecular acyltrans- ferase activity, transferring several N-octanoyl- dl-amino acids to N-octanoyl-hydroxylamine. This acyltransfer ability of polymyxin acylase offers a new method of enzymic N-acylation of compounds containing amino components.     

Purification and characterization of a novel O-methyltransferase from Flammulina velutipes

An enzyme catalyzing the methylation of phenolic hydroxyl groups in polyphenols was identified from mycelial cultures of edible mushrooms to synthesize O-methylated polyphenols. Enzyme activity was measured to assess whether methyl groups were introduced into (?)-epigallocatechin-3-O-gallate (EGCG) using SAM as a methyl donor, and (?)-epigallocatechin-3-O-(3-O-methyl)-gallate (EGCG3″Me), (?)-epigallocatechin-3-O-(4-O-methyl)-gallate (EGCG4″Me), and (?)-epigallocatechin-3-O-(3,5-O-dimethyl)-gallate (EGCG3″,5″diMe) peaks were detected using crude enzyme preparations from mycelial cultures of Flammulina velutipes. The enzyme was purified using chromatographic and two-dimensional electrophoresis. The purified enzyme was subsequently analyzed on the basis of the partial amino acid sequence using LC–MS/MS. Partial amino acid sequencing identified the 17 and 12 amino acid sequences, VLEVGTLGGYSTTWLAR and TGGIIIVDNVVR. In database searches, these sequences showed high identity with O-methyltransferases from other mushroom species and completely matched 11 of 17 and 9 of 12 amino acids from five other mushroom O-methyltransferases.     

Expression of recombinant alpha and beta tubulins from the yew Taxus cuspidata and analysis of the microtubule assembly in the presence of taxol

Taxol was originally isolated from the yew Taxus brevifolia. Because taxol inhibits the depolymerization of microtubules, the presence of a self-resistance mechanism in Taxus spp. was hypothesized. The cloning of the cDNA for alpha and beta tubulins from Taxus cuspidata and those from the human embryonic kidney cell line HEK293T revealed that the ²⁶Asp, ³⁵⁹Arg, and ³⁶¹Leu residues in the human beta tubulin, which are important for taxol binding, were replaced with Glu, Trp, and Met in the beta tubulin of T. cuspidata, respectively. The microtubule assembly of the recombinant alpha and beta tubulins was monitored turbidimetrically, and the results clearly demonstrated that the microtubule from T. cuspidata is less sensitive to taxol than that from HEK293T cells. The Taxus microtubule composed of the wild-type alpha tubulin and the beta tubulin with the E26D mutation restored the sensitivity to taxol. We thus postulated that the mutation identified in the beta tubulin of T. cuspidata plays a role in the self-resistance of this species against taxol.     

Potentiation of the early-phase insulin response by a prior meal contributes to the second-meal phenomenon in type 2 diabetes

Improved glucose tolerance following a sequential meal is known as the second-meal phenomenon. We aimed to investigate its extent and underlying mechanisms in patients with type 2 diabetes. Metabolic responses after lunch in 12 diabetic patients were compared on two separate days: one with (Day BL) and another without (Day FL) breakfast. The responses of hormones were calculated by the incremental area under the curve (iAUC) values for 180 min after each meal. Indexes of early-phase insulin secretion were assessed, and β-cell function was estimated by mathematical modeling. [iAUC(glucose(180-360 min))] was significantly lower on Day BL than on Day FL (181 ± 43 vs. 472 ± 29 mmol·liter(-1)·min, P = 0.0005). The magnitude of the The second-meal phenomenon [iAUC(glucose(180-360 min)) on Day BL/Day FL] was 35 ± 9%. The peak levels of insulin and C-peptide were attained 45 min earlier after the second meal than after the first meal. iAUC(glucose(180-360 min)) correlated negatively with iAUC(insulin(180-210 min)) (r = -0.443, P = 0.0300), insulinogenic index (r = -0.769, P < 0.0001), acute C-peptide response (r = -0.596, P = 0.0021), and potentiation factor [i.e., potentiation effect on insulin secretion] ratio (180-360)/(0-20) (r = -0.559, P = 0.0045), while correlated positively with free fatty acid level before lunch (r = 0.679, P = 0.0003). The second-meal phenomenon was evident in patients with type 2 diabetes. Potentiation of the early-phase insulin response by a prior meal contributes to this phenomenon in type 2 diabetes.     

The emergent role of sarcopenia: Preliminary Report of the Observatory of Sarcopenia of the Spanish Society of Geriatrics and Gerontology

Sarcopenia is a common and prominent geriatric syndrome, of major interest for daily clinical practice of professionals working with older people. The number of affected individuals and its relation with disability, frailty, many chronic diseases, lifestyle and adverse outcomes are extremely relevant for geriatric care. Moreover, biological changes that lead to the loss of muscle mass and strength are intrinsically related to the mechanisms of aging. It is not therefore surprising that research in this field is growing exponentially in recent years, and sarcopenia has been placed in recent years in the forefront of research in geriatric medicine and gerontology. The Spanish Society of Geriatrics and Gerontology has recently created an Observatory of Sarcopenia, which aims to promote educational and research activities in this field. The first activity of the Observatory has been to offer the Spanish speaking scientific community a review of the current status of sarcopenia, that may allow unifying concepts and fostering interest in this promising field of geriatrics.     

La eclosión de la sarcopenia: Informe preliminar del Observatorio de la Sarcopenia de la Sociedad Española de Geriatría y Gerontología

Sarcopenia is a common and prominent geriatric syndrome, of major interest for daily clinical practice of professionals working with older people. The number of affected individuals and its relation with disability, frailty, many chronic diseases, lifestyle and adverse outcomes are extremely relevant for geriatric care. Moreover, biological changes that lead to the loss of muscle mass and strength are intrinsically related to the mechanisms of aging. It is not therefore surprising that research in this field is growing exponentially in recent years, and sarcopenia has been placed in recent years in the forefront of research in geriatric medicine and gerontology.The Spanish Society of Geriatrics and Gerontology has recently created an Observatory of Sarcopenia, which aims to promote educational and research activities in this field. The first activity of the Observatory has been to offer the Spanish speaking scientific community a review of the current status of sarcopenia, that may allow unifying concepts and fostering interest in this promising field of geriatrics.     

Inhibition of autophagy by TAB2 and TAB3

Autophagic responses are coupled to the activation of the inhibitor of NF-κB kinase (IKK). Here, we report that the essential autophagy mediator Beclin 1 and TGFβ-activated kinase 1 (TAK1)-binding proteins 2 and 3 (TAB2 and TAB3), two upstream activators of the TAK1-IKK signalling axis, constitutively interact with each other via their coiled-coil domains (CCDs). Upon autophagy induction, TAB2 and TAB3 dissociate from Beclin 1 and bind TAK1. Moreover, overexpression of TAB2 and TAB3 suppresses, while their depletion triggers, autophagy. The expression of the C-terminal domain of TAB2 or TAB3 or that of the CCD of Beclin 1 competitively disrupts the interaction between endogenous Beclin 1, TAB2 and TAB3, hence stimulating autophagy through a pathway that requires endogenous Beclin 1, TAK1 and IKK to be optimally efficient. These results point to the existence of an autophagy-stimulatory 'switch' whereby TAB2 and TAB3 abandon inhibitory interactions with Beclin 1 to engage in a stimulatory liaison with TAK1.     

<Emphasis Type="Italic">In silico</Emphasis> prediction of horizontal gene transfer in <Emphasis Type="Italic">Streptococcus thermophilus</Emphasis>

A combination of gene loss and acquisition through horizontal gene transfer (HGT) is thought to drive Streptococcus thermophilus adaptation to its niche, i.e. milk. In this study, we describe an in silico analysis combining a stochastic data mining method, analysis of homologous gene distribution and the identification of features frequently associated with horizontally transferred genes to assess the proportion of the S. thermophilus genome that could originate from HGT. Our mining approach pointed out that about 17.7% of S. thermophilus genes (362 CDSs of 1,915) showed a composition bias; these genes were called ‘atypical’. For 22% of them, their functional annotation strongly support their acquisition through HGT and consisted mainly in genes encoding mobile genetic recombinases, exopolysaccharide (EPS) biosynthesis enzymes or resistance mechanisms to bacteriophages. The distribution of the atypical genes in the Firmicutes phylum as well as in S. thermophilus species was sporadic and supported the HGT prediction for more than a half (52%, 189). Among them, 46 were found specific to S. thermophilus. Finally, by combining our method, gene annotation and sequence specific features, new genome islands were suggested in the S. thermophilus genome.