There are no letter designated codes as such for tax although some employers use N to designate "normal" or not emergency or week 1 based. I cannot comment on the A on your wife as there is no A tax code in Ireland. The PRSI A1 is the standard PRSI code for anyone earning in excess of €500 per week.
A Couple may earn €72,800 between them in 2009 at the standard (20% rate). You may split this between you anyway provided neither may have more than €45,400. This is what you have. However if your wife is earning less than €45,400 and you are earning more than €27,400 you may benefit from a re-distribution of the standard rate cut-off point as you could be paying tax at 41% on the excess over €27,400 and she would have spare capacity at 20%.