d-Xylulose kinase from Saccharomyces cerevisiae: Isolation and characterization of the highly unstable enzyme, recombinantly produced in Escherichia coli

► Xylulose kinase (XKS1) is a key enzyme for xylose utilization in Saccharomyces cerevisiae. ► XKS1 was recombinantly produced in E. coli, and native and tagged forms of the enzyme were isolated. ► XKS1 was highly unstable, losing its activity rapidly during purification or storage. ► Isolated XKS1 was shown by MS to be structurally intact. ► XKS1 harboring a C-terminal Strep-tag II was purified with retention of activity and characterized.