Biomedical Engineering Reference
In-Depth Information
O
H
3
C
CH
3
O
H
O
OH
OH
H
3
C
CH
3
CH
3
OH
OH
Sugar
H
3
C
O
OCH
3
O
H
Sugar
CH
3
Sugar
O
CH
3
Erythromycin
Daunorubicin
OCH
3
HO
OCH
3
O
CH
3
O
CH
3
H
3
C
H
H
O
O
H
O
CH
3
H
3
C
H
O
H
H
3
C
CH
3
OO
H
OH
O
CH
3
H
OCH
3
Avermectin
O
O
CH
3
HC
H
3
C
H
3
C
Sugar
Sugar
O
OH
O
CH
3
Fig. 14.18
Some examples of
polyketides.
Tylosin
as polyketides. These molecules, which are syn-
thesized by actinomycetes, have a fairly complex
structure (Fig. 14.18). The genes involved in the
biosynthesis of polyketides are clustered, thereby
facilitating the cloning of all of the genes controlling
the synthetic pathway. The first cluster (the
act
genes)
to be cloned was that for actinorhodin. When parts
of the
act
gene cluster were introduced into strepto-
mycetes making related polyketides, completely new
antibiotics were produced (Hopwood
et al.
1985).
For example, introducing the
actVA
gene from
Strep-
tomyces coelicolor
into a strain that makes medermycin
leads to the synthesis of mederrhodinA (Fig. 14.19).
This approach has been repeated many times since
