Is the occurrence of a particular enzyme in a given subcellular location a random phenomenon?
There are various methods for targetting proteins to subcellular organelles or membrane locations. In general they depend on ‘tagging’ or ‘signal’ sequences in the proteins. Such tags or signals are recognized by specialized proteins that are able to conduct the protein through the membrane barrier to the particular location. 

The individual processes for different target locations vary, so I do not think it appropriate to provide details here. You can read a summary of them in this Wikipedia article. For more extensive treatment you can look at the relevant chapters in Lodish et al.  or in Alberts et al. on-line (old edition).

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