Purification, properties and synthesis of delta-aminolaevulinate dehydratase from Neurospora crassa

Metabolic comparison of aerial and submerged mycelia formed in the liquid surface culture of Cordyceps militaris

An entomopathogenic fungus, Cordyceps sp. has been known to produce cordycepin which is a purine nucleoside antimetabolite and antibiotic with potential anticancer, antioxidant and anti-inflammatory activities. Interestingly, Cordyceps militaris produces significantly higher amount in a liquid surface culture than in a submerged culture. The liquid surface culture consists of mycelia growing into the air (aerial mycelia) and mycelia growing toward the bottom into the medium (submerged mycelia). In this study, to clarify roles of aerial and submerged mycelia of C. militaris in the cordycepin production the difference in metabolism between these mycelia was investigated. From transcriptomic analyses of the aerial and submerged mycelia at the culture of 5, 12 and 19 days, the metabolism of the submerged mycelia switched from the oxidative phosphorylation to the fermentation pathway. This activated the pentose phosphate pathway to provide building block materials for the nucleotide biosynthetic pathway. Under hypoxic conditions, the 5-aminolevulinic acid synthase (CCM_01504), delta-aminolevulinic acid dehydratase (CCM_00935), coproporphyrinogen III oxidase (CCM_07483) and cytochrome c oxidase 15 (CCM_05057) genes of heme biosynthesis were significantly upregulated. In addition, the liquid surface culture revealed that metabolite coproporhyrinogen III and glycine, the product and precursor of heme, were increased at 12th day and decreased at 19th day, respectively. These results indicate that the submerged mycelia induce the activation of iron acquisition, the ergosterol biosynthetic pathway, and the iron cluster genes of cordycepin biosynthesis in a hypoxic condition. Even though, the expression of the cluster genes of cordycepin biosynthesis was not significantly different in both types of mycelia.

Heme biosynthesis and its regulation: towards understanding and improvement of heme biosynthesis in filamentous fungi

Heme biosynthesis in fungal host strains has acquired considerable interest in relation to the production of secreted heme-containing peroxidases. Class II peroxidase enzymes have been suggested as eco-friendly replacements of polluting chemical processes in industry. These peroxidases are naturally produced in small amounts by basidiomycetes. Filamentous fungi like Aspergillus sp. are considered as suitable hosts for protein production due to their high capacity of protein secretion. For the purpose of peroxidase production, heme is considered a putative limiting factor. However, heme addition is not appropriate in large-scale production processes due to its high hydrophobicity and cost price. The preferred situation in order to overcome the limiting effect of heme would be to increase intracellular heme levels. This requires a thorough insight into the biosynthetic pathway and its regulation. In this review, the heme biosynthetic pathway is discussed with regards to synthesis, regulation, and transport. Although the heme biosynthetic pathway is a highly conserved and tightly regulated pathway, the mode of regulation does not appear to be conserved among eukaryotes. However, common factors like feedback inhibition and regulation by heme, iron, and oxygen appear to be involved in regulation of the heme biosynthesis pathway in most organisms. Therefore, they are the initial targets to be investigated in Aspergillus niger.

Studies of hybrid hematopoietic growth factor receptors

To gain further insight into the mechanisms by which both granulocyte-macrophage-colony stimulating factor (GM-CSF) and erythropoietin receptors function, we have utilized a GM-CSF erythropoietin hybrid receptor with GM-CSF as the external domain and erythropoietin as the intracellular domain. Results show that the beta common GM-CSF receptor both enhances the affinity binding of GM-CSF to the receptor and plays an important role in signaling through the receptor. A truncated form of the beta common receptor actually acts as a dominant negative regulatory factor.

Purification and characterization of animal porphobilinogen synthases--II. Dog liver porphobilinogen synthase

1. A method is described for the purification of porphobilinogen synthase (PBG-S) from dog liver (acetone dry powder; ammonium sulfate fractionation; controlled heat denaturation; ion exchange chromatography; gel filtration). The 911-fold purified enzyme with a specific activity of 372 mU/mg and 6.2 nkat/mg enzyme protein, respectively, appears as a single band in disc electrophoresis. 2. The optimum pH of the enzyme is 6.8; the Michaelis constant Km = 1.77 x 10(-4) M with 5-amino-levulinic acid as substrate. 3. The determination of the molecular weight of the native multisubunit enzyme (268,000 dalton) and of the subunit (33,500 dalton) are in favour of an octameric structure. 4. The acyl group blocking the N-terminus has been identified as an acetyl group (hydrazinolysis; dansylation; TLC; HPLC). 5. The amino acid composition of the PBG-S subunit is as follows CH3CO-NH-(Asx22Thr9-10Ser18Glx28-29Pro20-21Gly22Ala35-37Val23-25Met5 Ile8-9Leu32-33Tyr10Phe12Lys12Cys3His7Arg22Trp3)-Ala-Leu-COOH. 6. In the presence of ganidinium chloride only one free sulfhydryl group per subunit (3 cysteine residues) could be detected. 7. The purified enzyme contains 0.56 gram atoms of zinc per octamer (neutron activating analysis).