Serine substitution for cysteine residues in levansucrase selectively abolishes levan forming activity.
Levansucrase is responsible for levan formation during sucrose fermentation of Zymomonas mobilis, and this decreases the efficiency of ethanol production. As thiol modifying agents decrease levan formation, a role for cysteine residues in levansucrase activity has been examined using derivatives of Z. mobilis levansucrase that carry serine substitutions of cysteine at positions 121, 151 or 244. These substitutions abolished the levan forming activity of levansucrase whilst only halving its activity in sucrose hydrolysis. Thus, polymerase and hydrolase activities of Z. mobilis levansucrase are separate and have different requirements for the enzyme's cysteine residues.
Department of Microbial Technology, Centre for Excellence in Genomic Sciences, School of Biological Sciences, Madurai Kamaraj University, Madurai-625021, India.
Velusamy
V
Senthilkumar
Stephen J W
SJ
Busby
Paramasamy
P
Gunasekaran
Velusamy
V
Senthikumar
Stephen J W
SJ
Bushby
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D003001:Cloning, Molecular / Q000379:methods; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005630:Fructans / Q000096:biosynthesis* / Q000235:genetics; D006602:Hexosyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015202:Protein Engineering / Q000379:methods*; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism; D017355:Zymomonas / Q000201:enzymology* / Q000235:genetics*
D005630:Fructans; D012694:Serine; D013395:Sucrose; C072599:levan; D006602:Hexosyltransferases; C021513:levansucrase; D003545:Cysteine