Pectinolytic yeasts from cold environments: novel findings of Guehomyces pullulans,Cystofilobasidium infirmominiatum and Cryptococcus adeliensis producing pectinases

One hundred and three yeasts isolated from soil samples from King George Island and Tierra del Fuego province were screened in relation with their capability to produce pectinolytic enzymes. Although all the yeasts showed well-developed colonies at 20 °C, only eight showed a clear halo around the colony, indicative of pectin degradation. A secondary screening demonstrated that only four yeasts were capable to produce pectinases at low temperatures (8 °C). It could be seen that the selected yeasts were able to grow and produce high levels of polygalacturonase activity when submerged fermentations were performed using pectin-containing fruit wastes as substrates. None of the strains produced neither lyase nor rhamnogalacturonan hydrolase activities. Regarding pectin esterase activity, it was only produced in lower amounts by G. pullulans 8E (0.022 U ml⁻¹). A TLC analysis of the substrate cleavage pattern of the pectinolytic systems was consistent with an endo-type activity. The clarification of apple juice was only accomplished by G. pullulans pectinolytic system, with a clarification of 80% (%T₆₅₀) using 4 U/ml of enzyme at 20 °C. As far as we concern this work describes for the first time the production of pectinases by the cold-adapted yeasts species Cystofilobasidium infirmominiatum, Cryptococcus adeliensis and G. pullulans.

     

An allosteric inhibitor of the human Cdc34 ubiquitin-conjugating enzyme

In the ubiquitin-proteasome system (UPS), E2 enzymes mediate the conjugation of ubiquitin to substrates and thereby control protein stability and interactions. The E2 enzyme hCdc34 catalyzes the ubiquitination of hundreds of proteins in conjunction with the cullin-RING (CRL) superfamily of E3 enzymes. We identified a small molecule termed CC0651 that selectively inhibits hCdc34. Structure determination revealed that CC0651 inserts into a cryptic binding pocket on hCdc34 distant from the catalytic site, causing subtle but wholesale displacement of E2 secondary structural elements. CC0651 analogs inhibited proliferation of human cancer cell lines and caused accumulation of the SCF(Skp2) substrate p27(Kip1). CC0651 does not affect hCdc34 interactions with E1 or E3 enzymes or the formation of the ubiquitin thioester but instead interferes with the discharge of ubiquitin to acceptor lysine residues. E2 enzymes are thus susceptible to noncatalytic site inhibition and may represent a viable class of drug target in the UPS.     

Comparative studies on the biochemical properties of the malic enzymes from Trypanosoma cruzi and Trypanosoma brucei

The construction of engineered bacterial cells with a reduced genome allows the investigation of molecular mechanisms that may be cryptic in wild-type strains and derivatives. Previously, a large-scale combined deletion mutant of Escherichia coli that lacked 29.7% of the parental chromosome was constructed by combining large chromosome deletions. In this work, we improved the system for making markerless-chromosomal deletions and obtained mutants with a genome that lacked up to 38.9% of the parental chromosome. Although the large-scale deletion mutants possessed genes needed for resistance to oxidative stress, including superoxide dismutase, catalase, and RpoS, they were sensitive to menadione, which induces reactive oxygen species during stationary phase. Small genome size did not necessarily correlate with greater sensitivity to menadione as several mutants with large deletions were more resistant to menadione. The sensitivity to menadione depended on whether the mutants were grown aerobically or anaerobically, suggesting that the mechanism governing menadione resistance depended on the oxygen tension of the growth medium. Further analysis of the large-scale deletion mutants should help identify the regulatory networks that are important for cellular defense against oxidative stress.     

Differences in the relationship between nightmares and coping with stress for Asians and Caucasians: A brief report.

In contrast to posttraumatic nightmares, some nightmares can also be idiopathic. Previous research indicates that nightmares may serve a beneficial function as there is a positive relationship between nightmares and “waking” coping strategies. As a result, nightmares may fit into a continuity of coping throughout the sleep/wake cycle. In the present analysis, the relationship between nightmares and one measure of coping was only significant for those who identified themselves as Asian when compared those who identified themselves as Caucasian. These results represent one of the first differences in nightmares between ethnic groups. Such research is important for understanding the role of idiopathic nightmares in coping and understanding the importance of ethnicity when presented with patients complaining of nightmares. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Plasma values of vitamin A and its binding proteins (retinol binding proteins and prealbumin), carotene, total cholesterol and HDL-cholesterol in subjects with breast carcinoma

In this study plasma levels of vitamin A, carotenoids, retinol binding protein (RBP), prealbumin (PA), HDL-and total cholesterol were determined in 33 subjects with breast cancer and compared to those of a group of healthy subjects previously described. Plasma levels of vitamin A and carotene were determined by a spectrophotometric method using trifluoroacetic acid, plasma RBP and PA by single radial immunodiffusion, and HDL-and total cholesterol by enzymatic colorimetry. Mean plasma values of vitamin A, carotene and HDL-cholesterol were lower (P less than 0.01) than in the control group, the same applies to the RBP and PA mean levels (P less than 0.05). On the contrary, the mean value of total cholesterol was higher (P less than 0.01) in the patients than in the control group. Vitamin A plasma levels were significantly related to RBP and PA. No significant statistical correlation was found between clinical stage and vitamin A plasma levels.     

Plasma levels of vitamin A and its protein vectors (RBP and PA), carotene, total cholesterol and HDL-cholesterol in patients with carcinoma of the cervix

In this study plasma levels of vitamin A, carotenoids, retinol binding protein (RBP), prealbumin (PA), HDL-and total cholesterol of 40 subjects with carcinoma of cervix uteri were determined and compared to those of the healthy female subjects described in our previous research. Plasma levels of vitamin A and carotene were determined by a spectrophotometric method using trifluoroacetic acid, plasma RBP and PA by single radial immunodiffusion, and HDL-and total cholesterol by enzymatic colorimetry. Plasma mean values of carotene, vitamin A, RBP and HDL-cholesterol were lower (P less than 0.01) than in the control group, and the same applies to the PA mean plasma level (P less than 0.05). On the contrary, total cholesterol mean value of the patients resulted to be higher (P less than 0.01) than in the control group. Vitamin A plasma levels were significantly related (P less than 0.01) to RBP and PA. No significant statistical correlation was found between the clinical stage and the histological grading and vitamin A plasma levels.     

Isolation of α and β Brain Tubulin Subunits after Alkaline Treatment of the Protein

We demonstrate here that brain purified tubulin can be dissociated into and subunits at pH > 10 and that the subunits can be separated by using the Triton X-114 phase separation system. After phase partition at pH > 10, tubulin but not tubulin behaves as a hydrophobic compound appearing in the detergent rich phase. After three extractions of the alkaline aqueous phase with Triton X-114, about 90% of the tubulin was recovered in the detergent rich phase. The hydrophobic behavior observed for tubulin after its dissociation at pH 11.5 was not due to an irreversible change of the protein, because when the detergent rich phase containing tubulin was diluted with a buffer solution at pH 7.3 and the solution allowed to partition again, -tubulin is recovered in the aqueous phase. The detergent in the aqueous phase of the and tubulin preparations can be removed up to 90% by 12 h dialysis. The and subunits of tubulin from kidney and liver behave, in this phase separation system, like those of brain tubulin.