Open AccessProperties of Aspergillus niger citrate synthase and effects of cit A overexpression on citric acid production 1
Author(s) -
Ruijter George J.G,
Panneman Henk,
Xu DingBang,
Visser Jaap
Publication year - 2000
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2000.tb08986.x
Subject(s) - aspergillus niger , citric acid , citrate synthase , chemistry , biochemistry , production (economics) , atp synthase , food science , microbiology and biotechnology , enzyme , biology , economics , macroeconomics
Using a combination of dye adsorption and affinity elution we purified Aspergillus niger citrate synthase to homogeneity using a single column and characterised the enzyme. An A. niger citrate synthase cDNA was isolated by immunological screening and used to clone the corresponding cit A gene. The deduced amino acid sequence showed high similarity to other fungal citrate synthases. After processing upon mitochondrial import, the calculated M r of A. niger citrate synthase is 48 501, which agrees well with the estimated molecular mass of the purified protein (48 kDa). In addition to an N‐terminal mitochondrial import signal, a peroxisomal target sequence (AKL) was found at the C‐terminus of the protein. Whether both signals are functional in vivo is not clear. Strains overexpressing cit A were made by transformation and cultured under citric acid‐producing conditions. Up to 11‐fold overproduction of citrate synthase did not increase the rate of citric acid production by the fungus, suggesting that citrate synthase contributes little to flux control in the pathway involved in citric acid biosynthesis by a non‐commercial strain.