Data/hora: 18/06/2024 11:34:51

Provedor de dados: 	5	
País: 	France	
Título: 	Spatial patterns of ectoenzymatic kinetics in relation to biogeochemical properties in the Mediterranean Sea and the concentration of the fluorogenic substrate used	
Autores: 	Van Wambeke, France; Pulido, Elvira; Catala, Philippe; Dinasquet, Julie; Djaoudi, Kahina; Engel, Anja; Garel, Marc; Guasco, Sophie; Barbara, Marie; Nunige, Sandra; Taillandier, Vincent; Zancker, Birthe; Tamburini, Christian.	
Data: 	2021	
Ano: 	2021	
Resumo: 	Ectoenzymatic activity, prokaryotic heterotrophic abundances and production were determined in the Mediterranean Sea. Sampling was carried out in the sub-surface, the deep chlorophyll maximum layer (DCM), the core of the Levantine intermediate waters and in the deeper part of the mesopelagic layers. Michaelis–Menten kinetics were assessed using a large range of concentrations of fluorogenic substrates (0.025 to 50 µM). As a consequence, Km (Michaelis–Menten half-saturation constant) and Vm (maximum hydrolysis velocity) parameters were determined for both low- and high-affinity enzymes for alkaline phosphatase, aminopeptidase (LAP) and β-glucosidase (βGLU). Based on the constant derived from the high-LAP-affinity enzyme (0.025–1 µM substrate concentration range), in situ hydrolysis of N proteins contributed 48 % ± 30 % to the heterotrophic bacterial nitrogen demand within the epipelagic layers and 180 % ± 154 % in the Levantine intermediate waters and the upper part of the mesopelagic layers. The LAP hydrolysis rate was higher than bacterial N demand only within the deeper layer and only when considering the high-affinity enzyme. Based on a 10 % bacterial growth efficiency, the cumulative hydrolysis rates of C proteins and C polysaccharides contributed on average 2.5 % ± 1.3  % to the heterotrophic bacterial carbon demand in the epipelagic layers sampled (sub-surface and DCM). This study clearly reveals potential biases in current and past interpretations of the kinetic parameters for the three enzymes tested based on the fluorogenic-substrate concentration used. In particular, the LAP / βGLU enzymatic ratios and some of the depth-related trends differed between the use of high and low concentrations of fluorogenic substrates.	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	https://archimer.ifremer.fr/doc/00642/75452/76268.pdf

https://archimer.ifremer.fr/doc/00642/75452/76269.pdf

https://archimer.ifremer.fr/doc/00642/75452/83086.pdf

https://archimer.ifremer.fr/doc/00642/75452/83088.pdf

DOI:10.5194/bg-18-2301-2021

https://archimer.ifremer.fr/doc/00642/75452/	
Editor: 	Copernicus GmbH	
Formato: 	application/pdf	
Fonte: 	Biogeosciences (1726-4189) (Copernicus GmbH), 2021 , Vol. 18 , N. 7 , P. 2301-2323	
Fonte: 	info:eu-repo/semantics/openAccess

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