Mac 10.10.5 throwing error sudo: gpasswd: command not found

Question

I have requirement to add jenkins user on mac mini to docker group and trying below

which sudo
/usr/bin/sudo

Not working

sudo gpasswd -a jenkins docker

Not working

/usr/bin/sudo gpasswd -a jenkins docker
sudo: gpasswd: command not found

And at .bash_profile entries

 export PATH="$PATH:/usr/local/bin/"
 export PATH="/usr/local/git/bin:/sw/bin/:/usr/local/bin:/usr/local/:/usr/local/sbin:/usr/local/mysql/bin:$PATH"
 export PATH=/usr/bin:/usr/sbin:/bin:/usr/local/bin:/sbin:/opt/x11/bin:$PATH

Current logged user is administrator on this Mac. I'm not sure what may be going wrong here ?

Thanks, Vikram