Synthesis of novel d-glucuronic acid fatty esters using Candida antarctica lipase in tert-butanol

Glucuronic acid n-alkyl esters, a novel class of promising biosurfactants and their corresponding glucose esters with the same side-chain length, were synthesized by direct esterification in a non-aqueous phase (tert-butanol) using an immobilized lipase.     

Learning and discrimination of individual cuticular hydrocarbons by honeybees (Apis mellifera)

In social insect colonies, recognition of nestmates, kinship, caste and reproductive status is crucial both for individuals and for the colony. The recognition cues used are thought to be chemical, with the hydrocarbons found on the cuticle of insects often cited as being particularly important. However, in honeybees (Apis mellifera) the role of cuticular hydrocarbons in nestmate recognition is controversial. Here we use the proboscis extension response (PER) conditioning paradigm to determine how well honeybees learn long-chain linear alkanes and (Z)-alkenes present on the cuticle of worker bees, and also how well they can discriminate between them. We found large differences both in learning and discrimination abilities with the different cuticular hydrocarbons. Thus, the tested hydrocarbons could be classified into those which the bees learnt and discriminated well (mostly alkenes) and those which they did not (alkanes and some alkenes). These well-learnt alkenes may constitute important compounds used as cues in the social recognition processes.     

Is 2-phosphoglycerate-dependent automodification of bacterial enolases implicated in their export?

We observed that in vivo and in vitro a small fraction of the glycolytic enzyme enolase became covalently modified by its substrate 2-phosphoglycerate (2-PG). In modified Escherichia coli enolase, 2-PG was bound to Lys341, which is located in the active site. An identical reversible modification was observed with other bacterial enolases, but also with enolase from Saccharomyces cerevisiae and rabbit muscle. An equivalent of Lys341, which plays an important role in catalysis, is present in enolase of all organisms. Covalent binding of 2-PG to this amino acid rendered the enzyme inactive. Replacement of Lys341 of E.coli enolase with other amino acids prevented the automodification and in most cases strongly reduced the activity. As reported for other bacteria, a significant fraction of E.coli enolase was found to be exported into the medium. Interestingly, all Lys341 substitutions prevented not only the automodification, but also the export of enolase. The K341E mutant enolase was almost as active as the wild-type enzyme and therefore allowed us to establish that the loss of enolase export correlates with the loss of modification and not the loss of glycolytic activity.     

Chronic High-Fat Diet Impairs Collecting Lymphatic Vessel Function in Mice

Lymphatic vessels play an essential role in intestinal lipid uptake, and impairment of lymphatic vessel function leads to enhanced adipose tissue accumulation in patients with lymphedema and in genetic mouse models of lymphatic dysfunction. However, the effects of obesity on lymphatic function have been poorly studied. We investigated if and how adipose tissue accumulation influences lymphatic function. Using a lymphatic specific tracer, we performed in vivo near-infrared (NIR) imaging to assess the function of collecting lymphatic vessels in mice fed normal chow or high-fat diet (HFD). Histological and whole mount analyses were performed to investigate the morphological changes in initial and the collecting lymphatic vessels. HFD was associated with impaired collecting lymphatic vessel function, as evidenced by reduced frequency of contractions and diminished response to mechanostimulation. Moreover, we found a significant negative correlation between collecting lymphatic vessel function and body weight. Whole mount analyses showed an enlargement of contractile collecting lymphatic vessels of the hind limb. In K14-VEGF-C mice, HFD resulted in a reduced spreading of the tracer within dermal lymphatic vessels. These findings indicate that adipose tissue expansion due to HFD leads to a functional impairment of the lymphatic vasculature, predominantly in collecting lymphatic vessels.     

The replication kinase Cdc7-Dbf4 promotes the interaction of the p150 subunit of chromatin assembly factor 1 with proliferating cell nuclear antigen

The coordination of chromatin assembly with DNA replication, which is essential for genomic stability, requires the combined activation of histone deposition with the firing of replication origins. We report here the direct interaction of chromatin assembly factor 1 (CAF1), a key factor involved in histone deposition, with the replication kinase Cdc7-Dbf4. We isolated a complex containing both the largest subunit of CAF1 (p150) and the Cdc7-Dbf4 kinase specifically in S phase and thus prove the existence of this interaction in vivo. We then show that the Cdc7-Dbf4 kinase efficiently phosphorylates p150. This event induces a change in p150 oligomerization state, which promotes binding to proliferating cell nuclear antigen (PCNA). Conversely, CAF1 recruitment is reduced in a PCNA/DNA loading assay using Cdc7-depleted extracts. Our data define p150 as a new target for this kinase with implications for the coordination between DNA replication and CAF1 functions.