I am applying for Ph.D. in US universities and for that I already wrote a professor with my CV, asking if he has any vacancy in this lab or not. His reply was positive and encouraged me to apply. So I applied via GradCAS. Now one of my articles has been published in a reputed journal(which could have been enriched my CV). So is it ok if I send the prospective supervisor my article to read? Will it enhance my chance to get accepted?
You probably submitted far too early. Typically, the way admissions work in the US is that a committee reviews the applications and meets to discuss them shortly after the deadline. There's really no reason to apply 5 months before the deadline, your application will sit there unread. There's no bonus for submitting early, and no decisions will be made until the deadline in fairness to all applicants. As you've encountered, your application materials can change between now and the deadline, with new publications to add to CVs, hopefully additional research experience between now and then to report on, etc.
Additionally, although you can converse with a potential supervisor, at this point the admissions process is probably being done at the program level. A potential supervisor might be able to put in a good word for you, but they are likely not the ones making any final decision about you being admitted.
I'd update your CV nearer the deadline and ask the program if you can change it then. Even if the online portal won't let you update it, I think they'd probably accept. It's fine to send a paper to a potential supervisor if you think they'd be interested, but that won't be an effective way to get it added to consideration of your application. Probably it will sit in the professor's inbox and they may or may not look at the paper.