Expression of a Cellobiohydrolase cDNA from the White Rot Fungus Irpex lacteus in Aspergillus oryzae

Characterization of two acetyltransferase genes in the pyripyropene biosynthetic gene cluster from Penicillium coprobium

Pyripyropenes potently and selectively inhibit acyl-CoA:cholesterol acyltransferase 2 (ACAT-2). Among multiple isomers of pyripyropene (A to R), pyripyropene A (PyA) has insecticidal properties in addition to its growth inhibition properties against human umbilical vein endothelial cells. Based on the predicted biosynthetic gene cluster of pyripyropene A, two genes (ppb8 and ppb9) encoding two acetyltransferases (ATs) were separately isolated and introduced into the model fungus Aspergillus oryzae, using the protoplast–polyethylene glycol method. The bioconversion of certain predicted intermediates in the transformants revealed the manner by which acetylation occurred in the biosynthetic pathway by the products expressed by these two genes (AT-1 and AT-2). The acetylated products detected by high-performance liquid chromatography (HPLC) in the extracts from AT-1 and AT-2 transformant clones were not present in the extract from the transformant clone with an empty vector. The HLPC charts of each bioconversion study exhibited high peaks at 12, 10.5 and 9 min, respectively. Further ultraviolet absorption and mass spectrometry analyses identified the products as PyE, PyO and PyA, respectively. AT-1 acetylated the C-1 of deacetyl-pyripyropene E (deAc-PyE), while AT-2 played an active role in acetylating the C-11 of 11-deAc-PyO and C-7 of deAc-PyA at two different steps of the biosynthetic pathway.

Structure of Regenerated Celluloses Treated with Ionic Liquids and Comparison of their Enzymatic Digestibility by Purified Cellulase Components

In this study, regenerated celluloses were prepared from microcrystalline cellulose (MCC) by treatment with three ionic liquids (ILs) having 1-ethyl-3-methylimidazolium (Emim) as the cation, and the IL N-(2-methoxyethyl)-N,N-diethyl-N-methylammonium alanine ([N221ME][Ala]), where the amino acid moiety is the anion. The crystal form of cellulose was transformed from cellulose I to cellulose II by dissolution with an IL and regeneration with anti-solvent. However, the crystallinity of the regenerated cellulose was different; the disordered chain region was increased in the order of [N221ME][Ala] < [Emim][OAc] < [Emim][DEP] < [Emim][Cl]. The monocomponent cellulase, especially endoglucanase, showed high hydrolyzing activity for regenerated cellulose compared with untreated cellulose. Furthermore, the degree of increase of hydrolyzing activity was almost coincident with the order of crystallinity. For the effective hydrolysis of cellulose treated with an IL, it is necessary to prepare the cellulase mixture containing an adequate ratio of each cellulase component according to crystal allomorph and the crystallinity of regenerated cellulose.

Transcriptional regulation of two endoglucanase-encoding genes (cel3A and cel4) from the wood-degrading basidiomycete Polyporus arcularius

In the current study, the genomic and cDNA clones encoding the endoglucanase (cel4) of Polyporus arcularius were sequenced and characterized. The amino acid sequence of Cel4 indicated that it is a glycosyl hydrolase family 5 protein. The expressions of the previously cloned endoglucanase cel3A and cel4 were induced by Avicel (microcrystalline cellulose) and cellopentaose but repressed by glucose, cellobiose, cellotriose, and cellotetraose. There was a low level of transcription of both genes regardless of the carbon source. These results suggest that P. arcularius cells constitutively express a very low level of cellulase that can degrade insoluble crystalline cellulose and that the transcription of cel3A and cel4 in the cells is induced by products produced by these endoglucanases such as cellooligosaccharides.