Download MendeleyMechanistic Studies of theStreptomyces bingchenggensisAldolase-Dehydratase: Implications for Substrate and Reaction Specificity in the Acetoacetate Decarboxylase-like Superfamily.
Mydy, L.S., Hoppe, R.W., Hagemann, T.M., Schwabacher, A.W., Silvaggi, N.R.(2019) Biochemistry 58: 4136-4147
- PubMed: 31524380
- DOI: https://doi.org/10.1021/acs.biochem.9b00652
- Primary Citation of Related Structures:
6EEJ - PubMed Abstract:
The acetoacetate decarboxylase-like superfamily (ADCSF) is a little-explored group of enzymes that may contain new biocatalysts. The low level of sequence identity (∼20%) between many ADCSF enzymes and the confirmed acetoacetate decarboxylases led us to investigate the degree of diversity in the reaction and substrate specificity of ADCSF enzymes. We have previously reported on Sbi00515, which belongs to Family V of the ADCSF and functions as an aldolase-dehydratase. Here, we more thoroughly characterize the substrate specificity of Sbi00515 and find that aromatic, unsaturated aldehydes yield lower K M and higher k cat values compared to those of other small electrophilic substrates in the condensation reaction. The roles of several active site residues were explored by site-directed mutagenesis and steady state kinetics. The lysine-glutamate catalytic dyad, conserved throughout the ADCSF, is required for catalysis. Tyrosine 252, which is unique to Sbi00515, is hypothesized to orient the incoming aldehyde in the condensation reaction. Transient state kinetics and an intermediate-bound crystal structure aid in completing a proposed mechanism for Sbi00515.
Organizational Affiliation:
Department of Chemistry and Biochemistry , University of Wisconsin-Milwaukee , 3210 North Cramer Street , Milwaukee , Wisconsin 53211 , United States.
