Glutamate dehydrogenase(GDH)plays an important role in the ammonium assimilation and nitrogen metabolism by catalyzing the reversible oxidative deamination of L-glutamate to a-ketoglutarate.In the present study,the potential functions of GDH in response to heat stress were explored in the scleractinian coral Pocillopora damicornis(designated as PdGDH).The cDNA of PdGDH contained an open reading frame of 1 611 bp encoding a polypeptide of 536 amino acids,which exhibited the highest sequence identity to GDH of Stylophora pistillata(96％identity),and the deduced PdGDH protein was predicted to contain one GdhA domain(from Va195 to Tyr525).The recombinant protein of PdGDH(rPdGDH)was expressed in Escherichia coli BL21(DE3)-Transetta,and its catalytic activity was measured under different temperatures,pH conditions and epigallocatechin-3-gallate(EGCG,a GDH inhibitor)concentrations.The purified rPdGDH only used reduced coenzyme nicotinamide adenine dinucleotide(NADH)as coenzyme,and its highest activity was observed at 35℃and pH 7.5,respectively.The rPdGDH activity was negatively correlated with the concentration of EGCG,and was inhibited by more than half(65％,P＜0.05)at 10-4 mol/L EGCG.No significant alteration of PdGDH mRNA expression was detected at 12 h after exposure to heat and ammonium(P＞0.05).Furthermore,the activities of NADH-GDH in the scleractinian coral P.damicornis increased significantly at 12 h after the heat and ammonium stress,and the NADH-GDH activity in the heat stress group(32.66 U/mg,P＜0.05)was significantly higher than that in the heat and ammonium stress group(11.26 U/mg).These results collectively suggested that PdGDH,as a homologue of glutamate dehydrogenase in the scleractinian coral P.damicornis,could respond to heat stress at the protein level,which would have ability to further promote ammonium assimilation to increase the heat acclimatization of the coral-Symbiodiniaceae symbiotic association.

Jia TANG;Wenqi CAI;Zhicong YAN;Zhongjie WU;Qianxi YANG;Zhi ZHOU

State Key Laboratory of Marine Resource Utilization in South China Sea,Key Laboratory of Tropical Hydrobiology and Biotechnology of Hainan Province,Hainan Aquaculture Breeding Engineering Research Center,Hainan University,Haikou 570228,China;Hainan Academy of Ocean and Fisheries Sciences,Haikou 570228,China

海洋湖沼学报（英文版）

[1]Jia TANG;Wenqi CAI;Zhicong YAN;Zhongjie WU;Qianxi YANG;Zhi ZHOU-.Involvement of the ammonium assimilation mediated by glutamate dehydrogenase in response to heat stress in the scleractinian coral Pocillopora damicornis)[J].海洋湖沼学报（英文版）,2022(05):2001-2011

scleractinian,damicornis,PdGDH,Stylophora,pistillata,Va195,Tyr525,rPdGDH,Symbiodiniaceae

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