Active Subunits of Transaldolase Bound to Sepharose Journal Articles uri icon

  •  
  • Overview
  •  
  • Research
  •  
  • Identity
  •  
  • Additional Document Info
  •  
  • View All
  •  

abstract

  • Individual subunits of yeast transaldolase were studied by the method of matrix‐bound derivatives. Native dimeric transaldolase was bound to Sepharose activated with low amounts of cyanogen bromide to give matrix‐bound transaldolase in which the majority of molecules were bound covalently via only one subunit. Exhaustive washing with 6 M guanidinium chloride and renaturation in triethanolamine‐EDTA buffer resulted in a derivative (bound‐subunit transaldolase) which retained 65% of the original protein and 63% of the original activity. This active form of transaldolase is more sensitive to 2 M urea than bound‐dimeric transaldolase. Bound‐subunit transaldolase is able to associate with “nascent” soluble transaldolase subunits generated in situ by diluting a small aliquot of guanidinium‐chloridedenatured transaldolase into a much larger volume of buffer. The ability of bound‐subunit derivative to pick up soluble “nascent” transaldolase subunits is highly specific and reaches a plateau level close to the original protein and activity content of bound transaldolase. The product of such treatment (bound‐renatured transaldolase) has properties virtually indistinguishable from those of bound transaldolase. These results indicate that individual subunits of transaldolase are catalytically active.Bound‐subunit transaldolase has Km values similar to those of the bound‐dimeric derivatives and can be inactivated with sodium borohydride in the presence of the substrate fructose 6‐phosphate. However, the pH profile of the subunit form is substantially altered suggesting a shift in the pKa of an essential protonated group from 9.2 to 8.6.

publication date

  • December 1973

has subject area