Thermodynamic analysis of Kex2 activity: The acylation and deacylation steps are potassium- and substrate-dependent

Author(s)

Antunes, Alyne Alexandrino ^[1] ; Passos Jesus, Larissa de Oliveira ^[1] ; Manfredi, Marcella Araujo ^[1] ; de Souza, Aline Aparecida ^[1] ; Marcondes Machado, Mauricio Ferreira ^[1] ; Moraes e Silva, Pamela ^[1] ; Icimoto, Marcelo Yudi ^[2] ; Juliano, Maria Aparecida ^[2] ; Juliano, Luiz ^[2] ; de Souza Judice, Wagner Alves ^[1]

Affiliation

^[1] Univ Mogi Das Cruzes UMC, Ctr Interdisciplinar Invest Bioquim, Av Candido Xavier Almeida & Souza 200, Sala 1S-15, BR-08780911 Mogi Das Cruzes, SP - Brazil

^[2] Univ Fed Sao Paulo, Escola Paulista Med, Dept Biofis, Rua Tres de Maio 100, BR-04044020 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: Biophysical Chemistry; v. 235, p. 29-39, APR 2018.
• Web of Science Citations: 1

Abstract

Kex2 is the prototype of a large family of eukaryotic subtilisin-related proprotein-processing proteases that cleave at sites containing pairs of basic residues. Here, we studied the effects of KCl on the individual rate constants of association, dissociation, acylation and deacylation and determined the thermodynamic parameters at each step of the Kex2 reaction. Potassium bound Kex2 with K-D = 20.3 mM. The order in which potassium entered the reaction system modified the effect of activation or inhibition, which depended on the size of the substrate. A possible allosteric potassium binding site at the S-6 subsite was involved in activation, and a distant site located between the catalytic domain and the P-domain was involved in inhibition. Potassium decreased the energetic barriers of almost all steps of catalysis. The acylation of Ac-PMYKR-AMC in the absence of potassium was the rate-limiting step. Therefore, for substrates containing a P-1-Arg, the deacylation step is not necessarily the rate-limiting event, and other residues at the P' positions may participate in controlling the acylation and deacylation steps. Thus, it is reasonable to conclude that potassium is involved in the processing of the alpha-mating factor that promotes Ca2+, mobilization by activating a high-affinity Ca2+-influx system to increase the cytosolic {[}Ca2+], resulting in the activation of channels that are essential for the survival of Saccharomyces cerevisine cells. (AU)

• FAPESP's process: 14/02205-1 - Study of kinetic behavior of convertases
• Grantee: Wagner Alves de Souza Júdice
• Support Opportunities: Regular Research Grants
• FAPESP's process: 15/11190-0 - Biochemical characterization of caspase-like involved in a cell cycle of simple eukariotic.
• Grantee: Mauricio Ferreira Marcondes Machado
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/25112-4 - Evaluation of modulators of the activity of proteases involved in pathological processes
• Grantee: Wagner Alves de Souza Júdice
• Support Opportunities: Regular Research Grants