Characterization of the dihydrolipoamide dehydrogenase from Streptococcus pneumoniae and its role in pneumococcal infection

Abstract

had an 85% reduction in a-galactosidase activity and showed virtually no transport of galactose into the cells, which can explain these phenotypic changes. The DLDH-negative bacteria produced only 50% of normal capsular polysaccharide, a phenotype that may be associated with impaired carbohydrate metabolism. IntroductionDihydrolipoamide dehydrogenases (DLDH; EC 1.8.1.4) are homodimeric flavoproteins that catalyse the NAD + -dependent reoxidation of dihydrolipoamide (DLA) in a number of multienzyme complexes (Perham et al., 1987;Carothers et al., 1989;Williams, 1992;de Kok et al., 1998). These complexes are primarily involved in the conversion of 2-oxo acids to their corresponding acyl-CoA derivative and are involved in important steps in aerobic and anaerobic metabolism (Carothers et al., 1989;de Kok et al., 1998). DLDH makes up the E3 component of the pyruvate dehydrogenase, 2-oxo glutarate dehydrogenase and branchedchain 2-oxo acid dehydrogenase complexes. Additionally, DLDH functions in the glycine cleavage multienzyme complex (where it is referred to as the L protein), as well as in the acetoin dehydrogenase complex in bacteria such as Bacillus subtilis, Clostridium magnum and Pelobacter carbinolicus (Wieland, 1983;Dietrichs and Andreesen, 1990;Kruger et al., 1994;Oppermann and Steinbuchel, 1994;Berg and de Kok, 1997;de Kok et al., 1998;Aevarsson et al., 1999;Huang et al., 1999).Even though the main function of DLDH is associated with its role in 2-oxo acid dehydrogenase complexes, the fact that DLDH is present in organisms that lack these complexes suggests that the enzyme may have additional functions (Danson et al., 1987;Danson, 1988a). Trypanosoma brucei as well as various archeabacteria exhibit simpler ways of converting 2-oxo acids, while still containing a DLDH enzyme (Danson et al., 1987;Danson, 1988b). This suggests that the DLDH must have a separate function in these organisms, and that this function is possibly retained in species in which the DLDH is also part of a 2-oxo acid dehydrogenase complex. Richarme and Heine (1986) and Richarme (1989) proposed that DLDH may be involved in regulation of the transport of galactose, maltose and ribose across the membrane of SummaryIn the present study, we have characterized the dihydrolipoamide dehydrogenase (DLDH) of Streptococcus pneumoniae and its role during pneumococcal infection. We have also demonstrated that a lack of DLDH results in a deficiency in a-galactoside metabolism and galactose transport. DLDH is an enzyme that is classically involved in the three-step conversion of 2-oxo acids to their respective acyl-CoA derivatives, but DLDH has also been shown to have other functions. The dldh gene was virtually identical in three pneumococcal strains examined. Besides the functional domains and motifs associated with this enzyme, analysis of the pneumococcal dldh gene sequence revealed the presence of an N-terminal lipoyl domain. DLDH-negative bacteria totally lacked DLDH activity, indicating that this gene encodes the only DLDH in S. pneumoniae. The...

Catabolite Control Protein A (CcpA) Contributes to Virulence and Regulation of Sugar Metabolism in Streptococcus pneumoniae

“…SP1128 has also been shown to bind plasminogen, thereby facilitating host invasion, and contributes to virulence potential (6,20). Some of the proteins that are derepressed in the ccpA strain are associated with sugar uptake (SP1580, SP2108) (50,60) and organic acid metabolism (SP0715, SP1588) (64,68).…”

Ohr (Organic Hydroperoxide Resistance Protein) Possesses a Previously Undescribed Activity, Lipoyl-dependent Peroxidase

“…This finding is relevant because antibiotic-resistant strains of pathogenic bacteria are increasingly prevalent (48), and several major classes of bactericidal antibiotics operate through the production of highly deleterious hydroxyl radicals in both Gram-negative and Gram-positive bacteria (49). Remarkably, lipoyl groups are essential for parasite survival in host cells (50,51) and for virulence (52). Indeed, the utilization of lipoylated proteins for Ohr reduction represents an emerging area of investigation (19) into the likelihood that specific proteins perform multiple catalytic functions to provide a means to regulate divergent processes, with a single molecular switch.…”

Lipoamide dehydrogenase mediates retention of coronin-1 on BCG vacuoles, leading to arrest in phagosome maturation

“…In Mtb and BCG, LpdC is the E3 component of the pyruvate dehydrogenase complex and it also forms an integral component of peroxynitrite reductase/ peroxidase, which was recently reported to be crucial for mycobacterial antioxidant defenses (Bryk et al, 2002;Rhee et al, 2005). Moreover, the in vivo relevance of LpdC as a potential bacterial virulence factor was demonstrated in Pneumococcus infection models where the lack of LpdC increased the sensitivity of the bacterium to oxidative stress and attenuated its survival in mice (Smith et al, 2002). These observations suggest the possibility that expression of LpdC in the phagosome might protect mycobacteria from the rapid production of reactive oxygen species, one of the crucial initial defense mechanisms of the host macrophage in response to ingested pathogens (Babior, 1995).…”