Use the ssh-keys resource to manipulate the ssh-keys on an individual or team account.
$users = new Bitbucket\API\Users();
$users->setCredentials(new Http\Message\Authentication\BasicAuth($bb_user, $bb_pass));
$users->sshKeys()->all($account_name);
$users->sshKeys()->create($account_name, 'key content', 'dummy key');
$users->sshKeys()->update($account_name, 12, 'key content');
$users->sshKeys()->get($account_name, 12);
$users->sshKeys()->delete($account_name, 12);