How to find out the energy gained from hydrolysis of Dimethylsulfoniopropionate?
When the literature refers to "hydrolysis" of DMSP, it is referring to the following cleavage reaction, even though no water is involved in the overall reaction:

DMSP --> DMS + acrylate + H+

See for example at page 156 of Biological and Environmental Chemistry of DMSP and Related Sulfonium Compounds: "hydrolysis of DMSP to DMS and acrylic acid".

For the above reaction:

$\Delta G = -11.8$ kcal/mol 

Source: MetaCyc Reaction: 4.4.1.3

This means 11.8 kilocalories (49.4 kilojoules) of energy are released for each mole of DMSP that reacts.