title: Diversity, abundance and characterization of ruminal cysteine phytases suggest their important role in phytate degradation.
abstract: A novel class of cysteine phytase showing ability to degrade phytate has recently been isolated from rumen bacteria. To expand our knowledge of this enzyme class, a total of 101 distinct cysteine phytase gene fragments were identified from the ruminal genomic DNA of Bore goats and Holstein cows, and most of them shared low identities (< 50%) with known sequences. By phylogenetic analysis, these sequences were separated into three clusters that showed substantial diversity. The two most abundant cysteine phytase genes of goat rumens were cloned and their protein products were characterized. Four findings were revealed based on our results. (i) Compared with soil and water environment, where β-propeller phytase is the most important phytate-degrading enzyme, cysteine phytase is the major phytate-degrading enzyme in the anaerobic ruminal environment. (ii) Cysteine phytase fragments in the rumen contents of goat and cow have the same diversity profile, although most of the sequences and their abundance differ in the two species. (iii) Each species has their respective high-abundance genes, which may play major roles for phytate degradation. (iv) Compared with previously reported cysteine phytases that have pH optimum at 4.5, the pH optima of the two most abundant secreted goat cysteine phytases are 6.5 and 6.0, which are within the pH range found in the rumens. This study provides valuable information about the diversity, abundance and enzymatic properties of the ruminal cysteine phytases and emphasizes the important role(s) of these cysteine phytases probably in the terrestrial cycle of phosphorus.
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Huoqing
authors.initials: H
authors.lastname: Huang
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Dawei
authors.initials: D
authors.lastname: Fu
authors.forename: Jianjie
authors.initials: J
authors.lastname: Luo
authors.forename: Zhongyuan
authors.initials: Z
authors.lastname: Li
authors.forename: Huiying
authors.initials: H
authors.lastname: Luo
authors.forename: Pengjun
authors.initials: P
authors.lastname: Shi
authors.forename: Peilong
authors.initials: P
authors.lastname: Yang
authors.forename: Qiyu
authors.initials: Q
authors.lastname: Diao
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
mesh_terms: D010832:6-Phytase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000201:enzymology*; D002417:Cattle; D003545:Cysteine / Q000032:analysis; D006041:Goats; D008969:Molecular Sequence Data; D010758:Phosphorus / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism*; D012417:Rumen / Q000382:microbiology*; D012988:Soil Microbiology
chemical_list: D010758:Phosphorus; D010833:Phytic Acid; D010832:6-Phytase; D003545:Cysteine