According to Bronsted Lowry concept, in given reaction, water will behave as :

${\mathrm{CH}}_2\mathrm{COOH}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{CH}}_3{\mathrm{COO}}^{\ominus }+{\mathrm{H}}_3{\mathrm{O}}^{\oplus }$

Here, in the reaction,

${\mathrm{CH}}_2\mathrm{COOH}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{CH}}_3{\mathrm{COO}}^{\ominus }+{\mathrm{H}}_3{\mathrm{O}}^{\oplus }$

There are two acids and two bases in this reaction. Also water in this reaction acts as weak acid.