The interactions in the carboxyl terminus of human 4-hydroxyphenylpyruvate dioxygenase are critical to mediate the conformation of the final helix and the tail to shield the active site for catalysis.

ABSTRACT: 4-Hydroxylphenylpyruvate dioxygenase (4-HPPD) is an important enzyme for tyrosine catabolism, which catalyzes the conversion of 4-hydroxylphenylpyruvate (4-HPP) to homogentisate. In the present study, human 4-HPPD was cloned and expressed in E. coli. The kinetic parameters for 4-HPP conversion were: k cat=2.2 ± 0.1 s(-1); and K m=0.08 ± 0.02 mM. Sequence alignments show that human 4-HPPD possesses an extended C-terminus compared to other 4-HPPD enzymes. Successive truncation of the disordered tail which follows the final α-helix resulted in no changes in the K m value for 4-HPP substrate but the k cat values were significantly reduced. The results suggest that this disordered C-terminal tail plays an important role in catalysis. For inspection the effect of terminal truncation on protein s

SUBMITTER: Lin JF 

PROVIDER: S-EPMC3739788 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature