Laptop supports 4GB dimms but not sure about at speeds of 1600, it'll have to depend on the mainboard. 1st gen i core cpu's memory controller supports 800/1066.
Crucial reckons 1600 is supported even with 1.35v sticks so good chance the ram you have considered should work but wont really know until you try it. They may default to 1066, as with your 1333 ram. 1.35v memory will run at 1.5v fine if that is what the laptop's mainboard sets them to, in case the question crosses your mind.
https://www.crucial.com/compatible-upgrade-for/asus/k52je
Can you run Cpuz and post pic of memory tab please (imgur can be used to upload images to here), and see what your current memory is actually running at, 1333 or did the laptop set them to 1066. This will sort of indicate if mainboard is capable of running faster memory than the cpu's default memory controller speed. Unless there's an option in the bios to set them, highly doubtful, but possibly is what you did if 1333 wasn't set automatically.
Upgrading to higher capacity dimms may require you to reset cmos. Possibility of improper boot if not do so. Try locate watch sized battery in case you need to do this.