title: Moonlighting protein in Starkeyomyces koorchalomoides: characterization of dihydrolipoamide dehydrogenase as a protein acetyltransferase utilizing acetoxycoumarin as the acetyl group donor.
abstract: In this report we have identified for the first time a transacetylase (TAase) in a mesophilic fungi Starkeyomyces koorchalomoides catalyzing the transfer of acetyl group from polyphenolic acetate (PA) to a receptor protein glutathione S-transferase (GST). An elegant assay procedure was established for TAase based on its ability to mediate inhibition of GST by 7,8-diacetoxy-4-methylcoumarin (DAMC), a model PA. Utilizing this assay procedure, S. koorchalomoides TAase was purified to homogeneity. TAase was found to have MW of 50 kDa. The purified enzyme exhibited maximum activity at 45 degrees C at pH 6.8. The N-terminal sequence of purified fungal TAase (ANDASTVED) showed identity with corresponding N-terminal sequence of dihydrolipoamide dehydrogenase (LADH), a mitochondrial matrix enzyme and an E3 component of pyruvate dehydrogenase complex (PDHC). TAase was found to have all the properties of LADH and avidly interacted with the anti-LADH antibody. TAase catalyzed acetylation of GST by DAMC was identified by LC-MS/MS and a single lysine residue (Lys-113) was found to be acetylated. Further, recombinant LADH from Streptococcus pneumoniae lacking lipoyl domain was found to exhibit little TAase activity, suggesting the role of lipoyl domain in the TAase activity of LADH. These observations bear evidence for the protein acetyltransferase activity of LADH. Such an activity of LADH can be attributed as a moonlighting function of the enzyme.
authors.affiliation: Department of Biochemistry, V. P. Chest Institute, University of Delhi, Delhi 110007, India.
authors.forename: Tapesh K
authors.initials: TK
authors.lastname: Tyagi
authors.forename: Prija
authors.initials: P
authors.lastname: Ponnan
authors.forename: Prabhjot
authors.initials: P
authors.lastname: Singh
authors.forename: Seema
authors.initials: S
authors.lastname: Bansal
authors.forename: Anoop
authors.initials: A
authors.lastname: Batra
authors.forename: Fabrice
authors.initials: F
authors.lastname: Collin
authors.forename: Francois
authors.initials: F
authors.lastname: Guillonneau
authors.forename: Daniel
authors.initials: D
authors.lastname: Jore
authors.forename: Shamkant A
authors.initials: SA
authors.lastname: Patkar
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Saxena
authors.forename: Virinder S
authors.initials: VS
authors.lastname: Parmar
authors.forename: Ramesh C
authors.initials: RC
authors.lastname: Rastogi
authors.forename: Hanumantharao G
authors.initials: HG
authors.lastname: Raj
mesh_terms: D000107:Acetylation; D000123:Acetyltransferases / Q000737:chemistry* / Q000235:genetics; D003374:Coumarins / Q000737:chemistry; D008058:Dihydrolipoamide Dehydrogenase / Q000737:chemistry* / Q000235:genetics; D005658:Fungi / Q000201:enzymology*; D005982:Glutathione Transferase / Q000737:chemistry; D013296:Streptococcus pneumoniae / Q000201:enzymology
chemical_list: C114369:7,8-diacetoxy-4-methylcoumarin; D003374:Coumarins; D008058:Dihydrolipoamide Dehydrogenase; D000123:Acetyltransferases; D005982:Glutathione Transferase