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Ectoine is a compatible solute and chemical chaperone widely used by members of the Bacteria and a few Archaea to fend-off the detrimental effects of high external osmolarity on cellular physiology and growth. Ectoine synthase (EctC) catalyzes the last step in ectoine production and mediates the ring closure of the substrate N-gamma-acetyl-L-2,4-diaminobutyric acid through a water elimination reaction. However, the crystal structure of ectoine synthase is not known and a clear understanding of how its fold contributes to enzyme activity is thus lacking. Using the ectoine synthase from the cold-adapted marine bacterium Sphingopyxis alaskensis (Sa), we report here both a detailed biochemical characterization of the EctC enzyme and the high-resolution crystal structure of its apo-form. Structural analysis classified the (Sa)EctC protein as a member of the cupin superfamily. EctC forms a dimer with a head-to-tail arrangement, both in solution and in the crystal structure. The interface of the dimer assembly is shaped through backbone-contacts and weak hydrophobic interactions mediated by two beta-sheets within each monomer. We show for the first time that ectoine synthase harbors a catalytically important metal co-factor; metal depletion and reconstitution experiments suggest that EctC is probably an iron-dependent enzyme. We found that EctC not only effectively converts its natural substrate N-gamma-acetyl-L-2,4-diaminobutyric acid into ectoine through a cyclocondensation reaction, but that it can also use the isomer N-alpha-acetyl-L-2,4-diaminobutyric acid as its substrate, albeit with substantially reduced catalytic efficiency. Structure-guided site-directed mutagenesis experiments targeting amino acid residues that are evolutionarily highly conserved among the extended EctC protein family, including those forming the presumptive iron-binding site, were conducted to functionally analyze the properties of the resulting EctC variants. An assessment of enzyme activity and iron content of these mutants give important clues for understanding the architecture of the active site positioned within the core of the EctC cupin barrel.

Background: Participation is often defined as taking part and being included in different areas of life. Leisure represents an important area of life for all people. People with disabilities have the right to experience leisure time in a self-determined manner. They have the right to participate in leisure activities on an equal basis with others. Due to various influencing factors, people with intellectual disabilities, especially those with severe to profound intellectual disabilities, are at risk of decreased participation. This is alarming because participation in leisure activities reflects quality of life. Purpose: The present study aims to review the empirical findings on leisure participation and its influencing factors in people with mild to moderate disabilities as compared to people with severe to profound intellectual disabilities. Method: A scoping review following the PRISMA-ScR checklist by Cochrane and the Joanna Briggs Institute (JBI) was conducted to examine research studies published in peer-reviewed journals between 2000 and 2022. The studies that were included relate to activities within the everyday leisure time of people with intellectual disabilities, regardless of age, gender, or severity of their cognitive disability. The categories of vacation and tourism were excluded so as to focus on everyday leisure. The sample was screened by two reviewers independently. In total, 27 articles met the inclusion criteria, with 21 articles referring to people with a mild to moderate intellectual disability and only six articles referring to people with a severe to profound intellectual disability. The evidence was summarized with a predefined standardized charting form, which was used by the two reviewers. Results: The results show that participation in leisure activities by people with intellectual disabilities can be limited, especially for those with severe to profound intellectual disabilities. This contradicts the guiding principle and human rights of inclusion and self-determination. Their participation in leisure time is extremely dependent on external factors, such as support people, leisure time availability, and form of living. Passive activities at home are often provided for people with severe to profound intellectual disabilities in particular; therefore, the need for interactive and self-determined leisure opportunities in the community is enormous. Various factors influencing leisure participation can be identified. Implications: The findings of this scoping review can be used to consider intervention, support, and barriers to enhancing leisure participation among people with disabilities as an important area of life.

This study examines the social position of N = 507 young people with and without intellectual disabilities (ID) in inclusive secondary classes, using a sociometric peer-rating method. In addition, their teachers (N = 21) were asked in topic-centred interviews about their subjective theories regarding the respective social position, as well as social dynamics management measures. It is shown that young people with special educational needs (SEN) have, on average, a significantly lower social position than those without SEN. Teachers justified this by means of (a) individual-related, (b) interaction-related, and (c) class level-related characteristics. The social dynamics management measures were related to the cooperation of teachers, the promotion of cooperation in the class, and the discourse on inclusion.

The structure of Igni18, ancient enzyme from the Crenarchaean species Ignicoccus hospitalis, is solved and characterized by Pérez-García, Chow and colleagues. This structure provides insight as to the evolution of metallo-beta-lactamases and their functions.

Biodegradation of synthetic polymers, in particular polyethylene terephthalate (PET), is of great importance, since environmental pollution with PET and other plastics has become a severe global problem. Here, we report on the polyester degrading ability of a novel carboxylic ester hydrolase identified in the genome of the marine hydrocarbonoclastic bacterium Pseudomonas aestusnigri VGXO14T. The enzyme, designated PE-H, belongs to the type IIa family of PET hydrolytic enzymes as indicated by amino acid sequence homology. It was produced in Escherichia coli, purified and its crystal structure was solved at 1.09 Å resolution representing the first structure of a type IIa PET hydrolytic enzyme. The structure shows a typical α/β-hydrolase fold and high structural homology to known polyester hydrolases. PET hydrolysis was detected at 30°C with amorphous PET film (PETa), but not with PET film from a commercial PET bottle (PETb). A rational mutagenesis study to improve the PET degrading potential of PE-H yielded variant PE-H (Y250S) which showed improved activity, ultimately also allowing the hydrolysis of PETb. The crystal structure of this variant solved at 1.35 Å resolution allowed to rationalize the improvement of enzymatic activity. A PET oligomer binding model was proposed by molecular docking computations. Our results indicate a significant potential of the marine bacterium P. aestusnigri for PET degradation.