Two isoforms of acetohydroxy acid synthase (AHAS), the first enzyme of the branched-chain amino acids biosynthetic pathway, were detected in cell-free extracts of the cyanobacterium Spirulina platensis and separated both by ion-exchange chromatography and by hydrophobic interaction. Several biochemical properties of the two putative isozymes were analysed and it was found that they differ for pH optimum, FAD requirement for both activity and stability, and for heat lability. The results were partially confirmed with the characterization of the enzyme extracted from a recombinant Escherichia coli strain transformed with one subcloned S. platensis coli strain transformed with one subcloned S. platensis AHAS gene. The approximate molecular mass of both AHAS activities, estimated by gel filtration, indicates that they are distinct isozymes and not different oligomeric species or aggregates of identical subunits.
Biochemical evidence for multiple forms of acetohydroxy acid synthase in Spirulina platensis
FORLANI, GIUSEPPE;RICCARDI, GIOVANNA;DE ROSSI, EDDA;
1991-01-01
Abstract
Two isoforms of acetohydroxy acid synthase (AHAS), the first enzyme of the branched-chain amino acids biosynthetic pathway, were detected in cell-free extracts of the cyanobacterium Spirulina platensis and separated both by ion-exchange chromatography and by hydrophobic interaction. Several biochemical properties of the two putative isozymes were analysed and it was found that they differ for pH optimum, FAD requirement for both activity and stability, and for heat lability. The results were partially confirmed with the characterization of the enzyme extracted from a recombinant Escherichia coli strain transformed with one subcloned S. platensis coli strain transformed with one subcloned S. platensis AHAS gene. The approximate molecular mass of both AHAS activities, estimated by gel filtration, indicates that they are distinct isozymes and not different oligomeric species or aggregates of identical subunits.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
