Biochemical characterization of adenosine deaminase (CD26; EC 3.5.4.4) activity in human lymphocyte-rich peripheral blood mononuclear cells. 2021

L R Costa, and A K Y de Souza, and J N Scholl, and F Figueiró, and A M O Battastini, and J A Dos Santos Jaques, and F F Zanoelo
Laboratório de Bioquímica Geral e de Microrganismos, Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, Campo Grande, MS, Brasil.

The conversion of adenosine to inosine is catalyzed by adenosine deaminase (ADA) (EC 3.5.4.4), which has two isoforms in humans (ADA1 and ADA2) and belongs to the zinc-dependent hydrolase family. ADA modulates lymphocyte function and differentiation, and regulates inflammatory and immune responses. This study investigated ADA activity in lymphocyte-rich peripheral blood mononuclear cells (PBMCs) in the absence of disease. The viability of lymphocyte-rich PBMCs isolated from humans and kept in 0.9% saline solution at 4-8°C was analyzed over 20 h. The incubation time and biochemical properties of the enzyme, such as its Michaelis-Menten constant (Km) and maximum velocity (Vmax), were characterized through the liberation of ammonia from the adenosine substrate. Additionally, the presence of ADA protein on the lymphocyte surface was determined by flow cytometry using an anti-CD26 monoclonal human antibody, and the PBMCs showed long-term viability after 20 h. The ADA enzymatic activity was linear from 15 to 120 min of incubation, from 2.5 to 12.5 µg of protein, and pH 6.0 to 7.4. The Km and Vmax values were 0.103±0.051 mM and 0.025±0.001 nmol NH3·mg-1·s-1, respectively. Zinc and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) inhibited enzymatic activity, and substrate preference was given to adenosine over 2'-deoxyadenosine and guanosine. The present study provides the biochemical characterization of ADA in human lymphocyte-rich PBMCs, and indicates the appropriate conditions for enzyme activity quantification.

UI MeSH Term Description Entries
D007963 Leukocytes, Mononuclear Mature LYMPHOCYTES and MONOCYTES transported by the blood to the body's extravascular space. They are morphologically distinguishable from mature granulocytic leukocytes by their large, non-lobed nuclei and lack of coarse, heavily stained cytoplasmic granules. Mononuclear Leukocyte,Mononuclear Leukocytes,PBMC Peripheral Blood Mononuclear Cells,Peripheral Blood Human Mononuclear Cells,Peripheral Blood Mononuclear Cell,Peripheral Blood Mononuclear Cells,Leukocyte, Mononuclear
D008214 Lymphocytes White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS. Lymphoid Cells,Cell, Lymphoid,Cells, Lymphoid,Lymphocyte,Lymphoid Cell
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000225 Adenine A purine base and a fundamental unit of ADENINE NUCLEOTIDES. Vitamin B 4,4, Vitamin B,B 4, Vitamin
D000243 Adenosine Deaminase An enzyme that catalyzes the hydrolysis of ADENOSINE to INOSINE with the elimination of AMMONIA. Adenosine Aminohydrolase,Aminohydrolase, Adenosine,Deaminase, Adenosine
D018819 Dipeptidyl Peptidase 4 A serine protease that catalyses the release of an N-terminal dipeptide. Several biologically-active peptides have been identified as dipeptidyl peptidase 4 substrates including INCRETINS; NEUROPEPTIDES; and CHEMOKINES. The protein is also found bound to ADENOSINE DEAMINASE on the T-CELL surface and is believed to play a role in T-cell activation. Antigens, CD26,CD26 Antigens,Dipeptidyl-Peptidase IV,Adenosine Deaminase Complexing Protein 2,CD26 Antigen,Antigen, CD26,Dipeptidyl Peptidase IV

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