The peroxisome: still a mysterious organelle

More than half a century of research on peroxisomes has revealed unique features of this ubiquitous subcellular organelle, which have often been in disagreement with existing dogmas in cell biology. About 50 peroxisomal enzymes have so far been identified, which contribute to several crucial metabolic processes such as β-oxidation of fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species, and render peroxisomes indispensable for human health and development. It became obvious that peroxisomes are highly dynamic organelles that rapidly assemble, multiply and degrade in response to metabolic needs. However, many aspects of peroxisome biology are still mysterious. This review addresses recent exciting discoveries on the biogenesis, formation and degradation of peroxisomes, on peroxisomal dynamics and division, as well as on the interaction and cross talk of peroxisomes with other subcellular compartments. Furthermore, recent advances on the role of peroxisomes in medicine and in the identification of novel peroxisomal proteins are discussed

Bioethanol: A New Synergy between Marine Chitinases from <i>Bacillus haynesii</i> and Ethanol Production by <i>Mucor circinelloides</i>

The fourth generation of bioethanol production is on a lookout for non-lignocellulosic biomass waste. One such candidate is chitin, the second most abundant biopolymer on earth. However, the crystalline nature of chitin hinders its application potential for bioethanol production. This limitation can be circumvented by hydrolysing this polymer into oligomers using chitinases. We used this hypothesis and isolated a Bacillus haynesii, a marine bacterium that utilizes colloidal chitin as a substrate and produces chitin oligosaccharides. Further, we utilized Mucor circinelloides to produce bioethanol using the chitin oligosaccharides in the shake flask. We investigated the effect of inoculum age, filling volume, different substrates, and substrate concentration on bioethanol production using Mucor circinelloides from Bacillus haynesii-produced chitin oligosaccharides. Bacillus haynesii demonstrated a maximum chitinase activity of 3.08 U/mL with specific activity of 96 U/mg at the 90th h. Chitin oligosaccharides produced by Bacillus haynesii were confirmed using mass spectrometry. Bioethanol concentration was determined using dichromate oxidation assay as well as gas chromatography. The research resulted in 7.4 g/L of ethanol from 30 g/L of chitin oligosaccharides, with a maximum ethanol yield of 0.25 g of ethanol/g substrate at the 55th h with 48 h inoculum in 80 mL of fermentation medium. Results suggest that chitin oligosaccharides from Bacillus haynesii are an effective and renewable substrate for bioethanol production

Binding of double-strand breaks in DNA by human Rad52 protein.

Double-strand breaks (DSBs) in DNA are caused by ionizing radiation. These chromosomal breaks can kill the cell unless repaired efficiently, and inefficient or inappropriate repair can lead to mutation, gene translocation and cancer. Two proteins that participate in the repair of DSBs are Rad52 and Ku: in lower eukaryotes such as yeast, DSBs are repaired by Rad52-dependent homologous recombination, whereas vertebrates repair DSBs primarily by Ku-dependent non-homologous end-joining. The contribution of homologous recombination to vertebrate DSB repair, however, is important. Biochemical studies indicate that Ku binds to DNA ends and facilitates end-joining. Here we show that human Rad52, like Ku, binds directly to DSBs, protects them from exonuclease attack and facilitates end-to-end interactions. A model for repair is proposed in which either Ku or Rad52 binds the DSB. Ku directs DSBs into the non-homologous end-joining repair pathway, whereas Rad52 initiates repair by homologous recombination. Ku and Rad52, therefore, direct entry into alternative pathways for the repair of DNA breaks