The effect of denaturants such as urea, guanidine hydrochloride,
sodium dodecyl sulfate, and heat on the activity of GI
from Arthrobacter and Streptomyces spp. was investigated (69,
131). The dissociation and unfolding of the tetrameric GI from
Streptomyces sp. strain NCIM 2730 revealed that the tetramer
and the dimer are the active species whereas the monomer is
inactive. The occurrence of a molten-globule-like intermediate
in the folding pathway of GI was demonstrated for the first
time (76). Intact tertiary rather than secondary structure was
shown to be responsible for the biological activity of GI.