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Kinetic characterization of P-type membrane ATPase from Streptococcus mutans
Prislaine P Magalhães1, Tony P Paulino, Geraldo Thedei
1Faculdade de Filosofia Ciências e Letras de Ribeirão Preto-FFCLRP-USP, Av. Bandeirantes 3900, Departamento de Química, 14040-901 Ribeirão Preto, SP, Brazil.
Summary
This study characterizes the P-type ATPase in Streptococcus mutans, crucial for managing cytoplasmic pH and acid resistance in dental caries. The enzyme exhibits unique kinetic properties, classifying it as type IIIA.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Proton translocating membrane ATPases in oral streptococci are vital for pH regulation, acid endurance, and cariogenicity.
- Streptococcus mutans is a primary species linked to dental caries.
- A P-type ATPase co-existing with F(1)F(o)-ATPase in S. mutans membranes has been identified.
Purpose of the Study:
- To kinetically characterize the ATP hydrolysis of the P-type ATPase in Streptococcus mutans.
- To understand the enzyme's kinetic properties and its role in bacterial physiology.
Main Methods:
- Enzyme kinetics assays were performed to determine ATP hydrolysis rates.
- The effects of varying ATP and magnesium ion concentrations were analyzed.
- The influence of various metal ions (Na+, K+, NH4+, Ca2+, Mg2+, Zn2+) and EDTA on enzyme activity was investigated.
Main Results:
- The optimal pH for ATP hydrolysis was determined to be approximately 6.0.
- The enzyme displayed positive cooperativity for ATP binding, with high (K(0.5)=0.27 mM) and low (K(0.5)=3.31 mM) affinity sites.
- Magnesium ions modulated activity similarly to ATP, with high (K(0.5)=0.10 mM) and low (K(0.5)=2.12 mM) affinity sites.
- Several ions (Na+, K+, NH4+, Ca2+, Mg2+) stimulated the enzyme, while Zn2+ and EDTA inhibited it.
Conclusions:
- The kinetic characteristics of the S. mutans P-type ATPase align with type IIIA ATPases, similar to those found in yeast and plants.
- This ATPase plays a significant role in the physiological functions of Streptococcus mutans, contributing to acid tolerance and cariogenicity.