|
KMID : 0545120010110061031
|
|
Journal of Microbiology and Biotechnology
2001 Volume.11 No. 6 p.1031 ~ p.1037
|
|
|
Expression Analysis of β-Ketothiolase and Acetoacetyl-CoA Reductase of Rhodobacter sphaeroides
|
|
Kho, Dhong Hyo
Jeong, Cheol Yun/Lee, Jeong Kug
|
|
|
Abstract
|
|
|
|
By a sequential action of β-ketothiolase and acetoacetyl-CoA reductase, two molecules of acetyl-CoA are converted into D-3-hydroxybutyryl-CoA, a substrate for PHB synthase to form poly-3-hydroxybutyrate (PHB) of Rhodobacter sphaeroides. The β-ketothiolase gene, phbA, and acetoacetyl-CoA reductase gene, phbB, were cloned and analyzed for their expression. Enzyme activities of β-ketothiolase and acetoacetyl-CoA reductase showed constitutive levels during aerobic and photoheterotrophic growth of R. sphaeroides. In addition, no difference of each enzyme activity was observed between cells grown aerobically and photoheterotrophically. The constitutive level of the enzyme activities are regulated at the level of phbAB transcription. Cellular PHB content, however, was reported as being regulated according to the growth phases along with growth conditions [15]. Thus, phbAB expression is not determinative in regulating the PHB content. On the other hand, phbA-deleted cell AZ1 accumulated only 10% PHB of the wild-type, and an elevated dosage of phbAB in trans in R. sphaeroides resulted in a higher content of PHB, indicating that phbAB codes for the enzymes responsible for providing the main supply of substrate for PHB synthase. PHB formation by an alternative pathway that does not depend on the phbA and phbB-coding enzymes is also proposed.
|
|
|
KEYWORD
|
|
|
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
  
|
|