Glutamate and Its Role in the Metabolism of Plants and Animals

Abstract

Glutamate is one of the major naturally occurring non-essential amino acids. The aim of this review is to provide a comprehensive analysis of the role of glutamate as a key metabolite in the metabolism of plant and animal organisms. Its role in nutrition and neurotransmission has intrigued researchers for many years. In both plants and animals, glutamate primarily exists in a monoanionic form characterised by unique physical and chemical properties. In plants, it is involved in the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle, while in animals, it plays a role in the glutamine/glutamate cycle, which is closely related to the urea cycle. Glutamate is also closely linked to the Krebs cycle in both groups of organisms through α-ketoglutarate. Glutamate is essential in both biosynthetic and catabolic pathways and participates in numerous physiological processes in plants and animals. Animals acquire glutamate from food, while plants acquire it from the soil; however, both also synthesise it de novo. Once present in the body, it is transported across cell membranes by specific transporters driven by ionic gradients (a mechanism known as secondary active transport). It is involved in cellular and systemic signalling pathways by interacting with ionotropic and metabotropic receptors. Additionally, glutamate is an important ‘building block’ of many proteins, including storage proteins. It also occurs in the form of monosodium glutamate (MSG), a flavour enhancer that is widely used but often criticised. Due to its important role in metabolism and signalling, the significance of glutamate in nutrition and its impact on human health are vital areas of research in food biochemistry. These investigations contribute to the development of nutritious food products and the design of effective pharmaceuticals. In this paper, we also address unresolved questions in glutamate research and consider its practical applications.