Alongside the binding to GABA receptors, some GABA undergoes reuptake and
some reach the glia with the help of GABA transporters. GABA which reaches
presynapse may be reused but those GABA entities that move to glia are metabolized to form succinic semialdehyde using GABA-Transaminase (GABA-T or EC
2.6.1.19) (Seigel et al. 1999; Rashmi et al. 2018).
24.1.1 Why is GABA Important?
GABA is considered to be an important inhibitory neurotransmitter because of the
pivotal role it plays in mammalian CNS. It has vital roles to play in neuronal
development, synaptic activities, counteracting depression and sleep disorders
(Ziskind-Conhaim 1998; Wong et al. 2003). Besides documented shreds of evidence for its activities on CNS, its innervation to other peripheral systems is also
considered crucial. GABA has proven to be effective anti-hypertensive, anti-cancer,
anti-oxidant, anti-obesity, anti-diabetic, tranquilizer, and many other effects are well
documented (Sheng et al. 2012; Teresa 2013; Injae et al. 2019; Shimada et al.
2009). Hence, the pharmaceutical applications of GABA give it an edge over other
neurotransmitters and its abundance in a variety of food products make it usable by
humans for health benefits. The enzyme GAD that catalyzes the conversion of
glutamate to GABA is found in many bacterial strains like Escherchia, Aspergillus,
Lactic acid bacteria, Neurospora etc. (Tavakoli et al. 2015; Diana et al. 2014). This
enzyme is also present in various plants such as soyabean, tomatoes, tea, germinated brown rice and also in few insects like flies, housefly and cockroaches (Diana
et al. 2014; Nikmaram et al. 2017). Scientists have been struggling hard to utilize
these microorganisms for GABA production through various technologies. The
levels of GABA may vary from trace quantity to micromolar range depending on
various factors. Despite of these low quantities present in plants, the pharmaceutical
and food industries and recently other manufacturing industries are paying strong
attention in increasing the concentration by various means. Several such techniques
include anoxia, enzymatic treatment, germination, old conventional methods,
microbial fermentation, use of excess glutamic acid and many more (Yongqi et al.
2018; Benincasa and Falcinelli 2019; Li et al. 2010a, b).
Very recent reports suggest that GABA is not only important from pharmaceutical and nutraceutical front but it is also important in industrial biotechnology
due to its need as a precursor for production of polymer called “Nylon 4” (Park
et al. 2013).
24.1.2 Alternative Synthetic Methods of GABA
Since biosynthesis of GABA does not always provide sufficient levels, it is
important to synthesize it by alternative methods. Hence, various synthetic methods
24 Advances and Perspectives of Gamma-Aminobutyric Acid …
821
some reach the glia with the help of GABA transporters. GABA which reaches
presynapse may be reused but those GABA entities that move to glia are metabolized to form succinic semialdehyde using GABA-Transaminase (GABA-T or EC
2.6.1.19) (Seigel et al. 1999; Rashmi et al. 2018).
24.1.1 Why is GABA Important?
GABA is considered to be an important inhibitory neurotransmitter because of the
pivotal role it plays in mammalian CNS. It has vital roles to play in neuronal
development, synaptic activities, counteracting depression and sleep disorders
(Ziskind-Conhaim 1998; Wong et al. 2003). Besides documented shreds of evidence for its activities on CNS, its innervation to other peripheral systems is also
considered crucial. GABA has proven to be effective anti-hypertensive, anti-cancer,
anti-oxidant, anti-obesity, anti-diabetic, tranquilizer, and many other effects are well
documented (Sheng et al. 2012; Teresa 2013; Injae et al. 2019; Shimada et al.
2009). Hence, the pharmaceutical applications of GABA give it an edge over other
neurotransmitters and its abundance in a variety of food products make it usable by
humans for health benefits. The enzyme GAD that catalyzes the conversion of
glutamate to GABA is found in many bacterial strains like Escherchia, Aspergillus,
Lactic acid bacteria, Neurospora etc. (Tavakoli et al. 2015; Diana et al. 2014). This
enzyme is also present in various plants such as soyabean, tomatoes, tea, germinated brown rice and also in few insects like flies, housefly and cockroaches (Diana
et al. 2014; Nikmaram et al. 2017). Scientists have been struggling hard to utilize
these microorganisms for GABA production through various technologies. The
levels of GABA may vary from trace quantity to micromolar range depending on
various factors. Despite of these low quantities present in plants, the pharmaceutical
and food industries and recently other manufacturing industries are paying strong
attention in increasing the concentration by various means. Several such techniques
include anoxia, enzymatic treatment, germination, old conventional methods,
microbial fermentation, use of excess glutamic acid and many more (Yongqi et al.
2018; Benincasa and Falcinelli 2019; Li et al. 2010a, b).
Very recent reports suggest that GABA is not only important from pharmaceutical and nutraceutical front but it is also important in industrial biotechnology
due to its need as a precursor for production of polymer called “Nylon 4” (Park
et al. 2013).
24.1.2 Alternative Synthetic Methods of GABA
Since biosynthesis of GABA does not always provide sufficient levels, it is
important to synthesize it by alternative methods. Hence, various synthetic methods
24 Advances and Perspectives of Gamma-Aminobutyric Acid …
821