Team:Osaka/Project pga

Gamma polyglutamic acid

OVERVIEW

Gamma polyglutamic acid (γ-PGA) is a very interesting biopolymer that attracts attention in late years.
It can be found in "natto", a Japanese traditional food , fermented soybeans. This healty food is very sticky.

In this sticky product secreted by Bacillus subtilis, γ-PGA is contained.γ-PGA and its derivatives offer a wide range of unique applications including being used as thickener, humectant, drug carrier, biodegradable fibers, highly water absorbable hydrogels, biopolymer flocculants, and heavy metal absorber. (Ing-Lung Shih et al,. 2001→)

PGA STRUCTURE

It is Dehydration-condensation reaction between gamma-position carboxyl group and alpha-position amino group of glutamate to compose PGA.
Glutamate have chirality. Although almost glutamate exist in L-form, PGA don't have only L-form Glutamate but also D-form Glutamate.

Poly glutamate synthetase

Poly glutamate synthetase(PGS) is necessary to produce PGA in Escherichia coli. PGS gene includes three ORF (open reading flame),which are pgsB, pgsC, and pgsA. These ORFs code three essential enzymes to create PGA.

PGA contains both D and L glutamate.

To increase the amount of PGA production, co-expression of glutamate racemase and PGS is needed.

PGS is originally localized in cell membrane, and proposed to produce PGA from D,L-Glutamic acid. Bacillus subtilis has enzymes to biodegrade PGA; however, E. coli does not. Therefore, we want E. coli to produce PGA for greening of the desert.