Diversification of the kinetic properties of yeast NADP‐glutamate‐dehydrogenase isozymes proceeds independently of their evolutionary origin

Abstract

In the yeast Saccharomyces cerevisiae, the ScGDH1 and ScGDH3 encoded glutamate dehydrogenases (NADP‐GDHs) catalyze the synthesis of glutamate from ammonium and α‐ketoglutarate (α‐KG). Previous kinetic characterization showed that these enzymes displayed different allosteric properties and respectively high or low rate of α‐KG utilization. Accordingly, the coordinated action of ScGdh1 and ScGdh3, regulated balanced α‐KG utilization for glutamate biosynthesis under either fermentative or respiratory conditions, safeguarding energy provision. Here, we have addressed the question of whether there is a correlation between the regulation and kinetic properties of the NADP‐GDH isozymes present in S. cerevisiae (ScGdh1 and ScGdh3), Kluyveromyces lactis (KlGdh1), and Lachancea kluyveri (LkGdh1) and their evolutionary history. Our results show that the kinetic properties of K. lactis and L. kluyveri single NADP‐GDHs are respectively similar to either ScGDH3 or ScGDH1, which arose from the whole genome duplication event of the S. cerevisiae lineage, although, KlGDH1 and LkGDH1 originated from a GDH clade, through an ancient interspecies hybridization event that preceded the divergence between the Saccharomyces clade and the one containing the genera Kluyveromyces, Lachancea, and Eremothecium. Thus, the kinetic properties which determine the NADP‐GDHs capacity to utilize α‐KG and synthesize glutamate do not correlate with their evolutionary origin.

Paralogs in the PKA regulon traveled different evolutionary routes to divergent expression in budding yeast

“…However, this simple story is often greatly complicated by the occurrence of gene conversion following WGH events when homologous genes overwrite all or part of their paralogs either soon after the polyploidization event or in the following millennia (Louis et al, 2012). It has been proposed that the functionally divergent ohnolog pair GDH1 and GDH3 experienced a gene conversion following the WGH (Campero-Basaldua et al, 2017). Our investigations of GND1/2 indicate that they might constitute another example of gene conversion.…”

The pleiotropic effects of the glutamate dehydrogenase (GDH) pathway in Saccharomyces cerevisiae

“…The NADP-dependent GDH enzyme in yeast is encoded by GDH1 and GDH3 [ 12 ]. GDH1 and GDH3 are paralogous genes with GDH3 originating from an ancestral event of whole-genome duplication [ 6 , 13 ] or interspecies hybridization [ 14 ]. Despite the high conservation of GDH1 and GDH3 , Gdh1p exhibits higher utilization rates of α-ketoglutarate under glucose conditions compared to Gdh3p [ 15 , 16 ].…”

“…This observation makes Gdh1 the primary (hyperbolic) NADP-GDH enzyme and Gdh3 the cooperative NADP-GDH isoform in the GDH pathway of S. cerevisiae. A recent study addressed the question whether the different utilization rates of α-ketoglutarate by Gdh1p and Gdh3p correlate with their evolutionary origin [ 6 ]. The authors compared the NADP-GDH activity of S. cerevisiae with that in closely related yeast species.…”

“…The kinetic properties of NADP-GDH activity that derived from yeast species with either constitutively respiratory metabolism, or intermediate fermentative capacity were similar to the Gdh1 and Gdh3 isoforms of S. cerevisiae and complemented the total NADP-GDH activity. Based on this it was concluded that the different utilization rates of α-ketoglutarate by Gdh1p and Gdh3p were independent of their evolutionary origin [ 6 ].…”

“…Central nitrogen metabolism in Saccharomyces cerevisiae hosts the same two conserved mechanisms for glutamate production [ 2 – 5 ]. GS–GOGAT pathway in yeast has a marginal contribution in glutamate synthesis both in fermentation and respiratory conditions, while the GDH pathway has the prominent role [ 5 , 6 ]. Yeast strains lacking the GDH route, present a proline utilization pathway (PUT) that can contribute together with the GS–GOGAT in glutamate biosynthesis and nitrogen assimilation [ 7 ].…”