So you're saying the tab button doesn't indent OR switch text box fields?
To answer you question.. NO there isn't a different button for macs.. tab should be working just as it would on a PC.
So.. to see if the tab button is functional at all I recommend hitting
Command + Tab..
when you do so this should come up..
if it doesn't than your tab key isn't working.. try rebooting... also try shift+tab and see if it will tab in reverse.
(btw command = the button by the space bar with an apple and a clover on it)