Ullah, A.H.J. and Gibson, D.M. (1987) Extracellular phytase (E.C. 3.1.3.8) from Aspergillus ficuum NRRL 3135: Purification and characterization. Preparative Biochemistr, 17, 63-91. doi:10.1080/00327488708062477

has been cited by the following article:

• TITLE: Elimination of a disulfide bridge in Aspergillus niger NRRL 3135 Phytase (PhyA) enhances heat tolerance and optimizes its temperature versus activity profile

  AUTHORS: Edward Mullaney, Kandan Sethumadhavan, Stephanie Boone, Xin Gen Lei, Abul H. J. Ullah

  KEYWORDS: Phytase; Disulfide Bridge; Aspergillus niger; Site-Directed Mutagenesis

  JOURNAL NAME: Advances in Biological Chemistry, Vol.2 No.4, November 23, 2012

  ABSTRACT: In this study, the optimum temperature was lowered while the residual phytase activity after heating to 70℃ was raised in a widely utilized phytase, Aspergillus niger NRRL 3135 PhyA. This was accomplished by site-directed mutagenesis of the cysteines that are involved in the formation of a single disulfide bridge (DB). When compared to wild type (WT), three of the four mutant phytases displayed a lower optimum temperature, 42℃, and up to a four-fold increase in activity after heating. These findings have a potentially broad application to be incorporated along with other desirable features to engineer a phytase with superior physical and chem-ical attributes for animal feed applications.