Enzymatic characterization of dihydrolipoamide dehydrogenase from Streptococcus pneumoniae harboring its own substrate

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift


This study describes the enzymatic characterization of dihydrolipoamide dehydrogenase (DLDH) from Streptococcus pneumoniae and is the first characterization of a DLDH that carries its own substrate (a lipoic acid covalently attached to a lipoyl protein domain) within its own sequence. Full-length recombinant DLDH (rDLDH) was expressed and compared with enzyme expressed in the absence of lipoic acid (rDLDH(-LA)) or with enzyme lacking the first 112 amino acids constituting the lipoyl protein domain (rDLDH(-LIPOYL)). All three proteins contained 1 mol of FAD/mol of protein, had a higher activity for the conversion of NAD(+) to NADH than for the reaction in the reverse direction, and were unable to use NADP(+) and NADPH as substrates. The enzymes had similar substrate specificities, with the K(m) for NAD(+) being approximately 20 times higher than that for dihydrolipoamide. The kinetic pattern suggested a Ping Pong Bi Bi mechanism, which was verified by product inhibition studies. The protein expressed without lipoic acid was indistinguishable from the wild-type protein in all analyses. On the other hand, the protein without a lipoyl protein domain had a 2-3-fold higher turnover number, a lower K(I) for NADH, and a higher K(I) for lipoamide compared with the other two enzymes. The results suggest that the lipoyl protein domain (but not lipoic acid alone) plays a regulatory role in the enzymatic characteristics of pneumococcal DLDH.


Enheter & grupper
Externa organisationer
  • University at Buffalo

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Infektionsmedicin
  • Cell- och molekylärbiologi


Sidor (från-till)29521-30
Antal sidor10
TidskriftJournal of Biological Chemistry
Utgåva nummer40
StatusPublished - 2007 okt 5
Peer review utfördJa