It has to do with verb conjugation rules, but has nothing to do with the subject's gender.
There are 3-4 types of regular verbs in Italian. The infinitive will end with -ARE, -ERE, or -IRE. If it's a regular verb, then all you do is remove the infinitive ending and replace it with the appropriate present tense ending for the subject.
So in the third person singular, if the infinitive is -ARE then it ends with -a, but if it's -ERE or -IRE then it ends with -e.