Human placenta cytidine deaminase: proton-linked enzyme activity and substrate binding.
In this work we focused our attention on some catalytic site requirements for human placenta cytidine deaminase (CDA). The effect of pH on substrate binding and catalysis was studied between pH 3.0 and pH 11.0. The results could be discussed postulating the presence of two classes of ionizable groups in the active site of CDA. The kinetic parameters pH-dependence has been discussed considering the presence of four zinc atoms per each enzyme tetramer. Furthermore fluorescence studies on the enzyme and on enzyme-inhibitor complexes, examined by using polar and non polar quenchers, allowed to define the substrate(inhibitor)-dependent accessibility of the tryptophan-containing pocket on each CDA monomer.
Vincenzetti
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S
Dipartimento di Biologia M.C.A, Università di Camerino, Italy.
Angeletti
M
M
Lupidi
G
G
Cambi
A
A
Natalini
P
P
Vita
A
A
D001665:Binding Sites; D002384:Catalysis; D003564:Cytidine Deaminase / Q000378:metabolism*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011485:Protein Binding; D011522:Protons; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D015032:Zinc
D011522:Protons; D003564:Cytidine Deaminase; D015032:Zinc