Phylogeny Tree Analysis Of Cellobiohydrolase I (CBHI)

Cellulose is one of the most abundant renewable biopolymer in nature, which can be hydrolyzed into large quantities of monosaccharides. Compared to physic and chemical methods, biological method of cellulose degradation has more advantages, such as mild reaction condition, low energy consumption and no pollution.Cellobiohydrolase I (CBHI) is an important exo-acting enzyme, playing a role in the conversion of cellulose to glucose by cutting the disaccharide cellobiose from the non-reducing end of the cellulose polymer chain. CBHI is composed of three parts: catalytic domain (CD), cellulose-binding domain (CBD) and a glycosylated linker peptide connecting CD and CBD. The CD of CBHI belongs to glycoside hydrolase family7(GH7) while the CBD belongs to carbohydrate-binding module family1(CBM1).Large quantities of CBHI related sequences are included in the searchable databases such as GenBank, providing reliable statistics for the research of CBHI. For the discovery of phylogenetic relationship between CBHI genes, this article collected CBHI coding statistics whose organisms were identified from databases and then did phylogeny tree analysis. The result showed that the length of collected sequences was1446-3032bp, the average length was1776bp and G+C content of them was49.44～65.65%, which indicated a high degree of genetic variation. The average transition/transversion rate ratio was0.71, thus the frequency of transversion was more than that of transition and CBHI genes were relatively active. The genetic distance between the sequences varied from0.003-0.697, showing that the degree of CBHI gene similarity between some species was low. So far acting as cellulose-degrading enzyme, CBHI genes have been found only in fungus, especially in Sordariomycetes, Eurotiomycetes and Agaricomycetes. While in other species there weren’t CBHI genes. The evolution of CBHI genes was quite related to the evolution of species.