Deciphering
the Biosynthetic Origin of l-<i>allo</i>-Isoleucine
Qinglian Li
Xiangjing Qin
Jing Liu
Chun Gui
Bo Wang
Jie Li
Jianhua Ju
10.1021/jacs.5b11380.s001
https://acs.figshare.com/articles/journal_contribution/Deciphering_the_Biosynthetic_Origin_of_l_i_allo_i_Isoleucine/2089135
The nonproteinogenic amino acid l-<i>allo</i>-isoleucine (l-<i>allo</i>-Ile) is featured in
an assortment of life forms comprised of, but not limited to, bacteria,
fungi, plants and mammalian systems including <i>Homo sapiens</i>. Despite its ubiquity and functional
importance, the specific origins of this unique amino acid have eluded
characterization. In this study, we describe the discovery and characterization
of two enzyme pairs consisting of a pyridoxal 5′-phosphate
(PLP)-linked aminotransferase and an unprecedented isomerase synergistically
responsible for the biosynthesis of l-<i>allo</i>-Ile from l-isoleucine (l-Ile) in natural products.
DsaD/DsaE from the desotamide biosynthetic pathway in <i>Streptomyces scopuliridis</i> SCSIO ZJ46, and
MfnO/MfnH from the marformycin biosynthetic pathway in <i>Streptomyces drozdowiczii</i> SCSIO 10141 drive l-<i>allo</i>-Ile generation in each respective system.
In vivo gene inactivations validated the importance of the DsaD/DsaE
pair and MfnO/MfnH pair in l-<i>allo</i>-Ile unit
biosynthesis. Inactivation of PLP-linked aminotransferases DsaD and
MfnO led to significantly diminished desotamide and marformycin titers,
respectively. Additionally, inactivation of the isomerase genes <i>dsaE</i> and <i>mfnH</i> completely abolished production
of all l-<i>allo</i>-Ile-containing metabolites
in both biosynthetic pathways. Notably, in vitro biochemical assays
revealed that DsaD/DsaE and MfnO/MfnH each catalyze a bidirectional
reaction between l-<i>allo</i>-Ile and l-Ile. Site-directed mutagenesis experiments revealed that the enzymatic
reaction involves a PLP-linked ketimine intermediate and uses an arginine
residue from the <i>C</i>-terminus of each isomerase to
epimerize the amino acid β-position. Consequently, these data
provide important new insight into the origins of l-<i>allo</i>-Ile in natural products with medicinal potential and
illuminate new possibilities for biotool development.
2016-01-13 00:00:00
bidirectional reaction
desotamide biosynthetic pathway
MfnO
marformycin biosynthetic pathway
arginine residue
vivo gene inactivations
Biosynthetic Origin
acid
ZJ
importance
isomerase synergistically
Streptomyce
origin
characterization
enzyme pairs
biotool development
aminotransferase
biosynthesi
life forms
isomerase genes dsaE
PLP
biosynthetic pathways
SCSIO
DsaD
marformycin titers