Lignocellulose degradation mechanisms across the Tree of Life.

Organisms use diverse mechanisms involving multiple complementary enzymes, particularly glycoside hydrolases (GHs), to deconstruct lignocellulose. Lytic polysaccharide monooxygenases (LPMOs) produced by bacteria and fungi facilitate deconstruction as does the Fenton chemistry of brown-rot fungi. Lignin depolymerisation is achieved by white-rot fungi and certain bacteria, using peroxidases and laccases. Meta-omics is now revealing the complexity of prokaryotic degradative activity in lignocellulose-rich environments. Protists from termite guts and some oomycetes produce multiple lignocellulolytic enzymes. Lignocellulose-consuming animals secrete some GHs, but most harbour a diverse enzyme-secreting gut microflora in a mutualism that is particularly complex in termites. Shipworms however, house GH-secreting and LPMO-secreting bacteria separate from the site of digestion and the isopod Limnoria relies on endogenous enzymes alone. The omics revolution is identifying many novel enzymes and paradigms for biomass deconstruction, but more emphasis on function is required, particularly for enzyme cocktails, in which LPMOs may play an important role.The work of the teams at York, Portsmouth and Cambridge on development of ideas expressed in this review was supported by grants from BBSRC (BB/H531543/1, BB/L001926/1, BB/1018492/1, BB/K020358/1). The workshop was supported by a US Partnering grant from BBSRC (BB/G016208/1) to Cragg and a BBSRC/FAPESP grant to Bruce (BB/1018492/1). Watts was supported by Marie Curie FP7-RG 276948. Goodell acknowledges support from USDA Hatch Project S-1041 VA-136288. Distel acknowledges support from NSF Award IOS1442759 and NIH Award Number U19 TW008163. Beckham thanks the US Department of Energy Bioenergy Technologies Office for funding. We appreciated the hospitality of the Linnean Society in allowing us to meet in inspirational surroundings under portraits of Linnaeus, Darwin and Wallace.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.cbpa.2015.10.01

Fungal GH25 muramidases : New family members with applications in animal nutrition and a crystal structure at 0.78Å resolution

Muramidases/lysozymes hydrolyse the peptidoglycan component of the bacterial cell wall. They are found in many of the glycoside hydrolase (GH) families. Family GH25 contains muramidases/lysozymes, known as CH type lysozymes, as they were initially discovered in the Chalaropsis species of fungus. The characterized enzymes from GH25 exhibit both β-1,4-N-acetyl- and β-1,4-N,6-O-diacetylmuramidase activities, cleaving the β-1,4-glycosidic bond between N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) moieties in the carbohydrate backbone of bacterial peptidoglycan. Here, a set of fungal GH25 muramidases were identified from a sequence search, cloned and expressed and screened for their ability to digest bacterial peptidoglycan, to be used in a commercial application in chicken feed. The screen identified the enzyme from Acremonium alcalophilum JCM 736 as a suitable candidate for this purpose and its relevant biochemical and biophysical and properties are described. We report the crystal structure of the A. alcalophilum enzyme at atomic, 0.78 Å resolution, together with that of its homologue from Trichobolus zukalii at 1.4 Å, and compare these with the structures of homologues. GH25 enzymes offer a new solution in animal feed applications such as for processing bacterial debris in the animal gut

Module walking using an SH3-like cell-wall-binding domain leads to a new GH184 family of muramidases

Muramidases (also known as lysozymes) hydrolyse the peptidoglycan component of the bacterial cell wall and are found in many glycoside hydrolase (GH) families. Similar to other glycoside hydrolases, muramidases sometimes have noncatalytic domains that facilitate their interaction with the substrate. Here, the identification, characterization and X-ray structure of a novel fungal GH24 muramidase from Trichophaea saccata is first described, in which an SH3-like cell-wall-binding domain (CWBD) was identified by structure comparison in addition to its catalytic domain. Further, a complex between a triglycine peptide and the CWBD from T. saccata is presented that shows a possible anchor point of the peptidoglycan on the CWBD. A `domain-walking' approach, searching for other sequences with a domain of unknown function appended to the CWBD, was then used to identify a group of fungal muramidases that also contain homologous SH3-like cell-wall-binding modules, the catalytic domains of which define a new GH family. The properties of some representative members of this family are described as well as X-ray structures of the independent catalytic and SH3-like domains of the Kionochaeta sp., Thermothielavioides terrestris and Penicillium virgatum enzymes. This work confirms the power of the module-walking approach, extends the library of known GH families and adds a new noncatalytic module to the muramidase arsenal

Molecular characterization of Arabidopsis thaliana cDNAs encoding three purine biosynthetic enzymes

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Risk for non-AIDS-defining and AIDS-defining cancer of early versus delayed initiation of antiretroviral therapy: A multinational prospective cohort study

Background: Immediate initiation of antiretroviral therapy (ART) regardless of CD4 cell count reduces risk for AIDS and non-AIDS-related events in asymptomatic, HIV-positive persons and is the standard of care. However, most HIV-positive persons initiate ART when their CD4 count decreases below 500 × 109 cells/L. Consequences of delayed ART on risk for non-AIDS-defining and AIDS-defining cancer, one of the most common reasons for death in HIV, are unclear. Objective: To estimate the long-term risk difference for cancer with the immediate ART strategy. Design: Multinational prospective cohort study. Setting: The D:A:D (Data collection on Adverse events of anti-HIV Drugs) study, which included HIV-positive persons from Europe, Australia, and the United States. Participants: 8318 HIV-positive persons with at least 1 measurement each of CD4 cell count and viral load while ART-naive (study period, 2006 to 2016). Measurements: The parametric g-formula was used, with adjustment for baseline and time-dependent confounders (CD4 cell count and viral load), to assess the 10-year risk for non-AIDS-defining and AIDS-defining cancer of immediate versus deferred (at CD4 counts < 350 and < 500 × 109 cells/L) ART initiation strategies. Results: During 64 021 person-years of follow-up, 231 cases of non-AIDS-defining cancer and 272 of AIDS-defining cancer occurred among HIV-positive persons with a median age of 36 years (interquartile range, 29 to 43 years). With immediate ART, the 10-year risk for non-AIDS-defining cancer was 2.97% (95% CI, 2.37% to 3.50%) and that for AIDS-defining cancer was 2.50% (CI, 2.37% to 3.38%). Compared with immediate ART initiation, the 10-year absolute risk differences when deferring ART to CD4 counts less than 500 × 109 cells/L and less than 350 × 109 cells/L were 0.12 percentage point (CI, -0.01 to 0.26 percentage point) and 0.29 percentage point (CI, -0.03 to 0.73 percentage point), respectively, for non-AIDS-defining cancer and 0.32 percentage point (CI, 0.21 to 0.44 percentage point) and 1.00 percentage point (CI, 0.67 to 1.44 percentage points), respectively, for AIDS-defining cancer. Limitation: Potential residual confounding due to observational study design. Conclusion: In this young cohort, effects of immediate ART on 10-year risk for cancer were small, and further supportive data are needed for non-AIDS-defining cancer. Primary Funding Source: Highly Active Antiretroviral Therapy Oversight Committee