HISTAMINOTRANS-RXN< group1 ATPPHOSPHORIBOSYLTRANS-RXN> group2 ATPPHOSPHORIBOSYLTRANS-RXN< group2 HISTALDEHYD-RXN> group3 HISTOLDEHYD-RXN> group3 HISTALDEHYD-RXN< group3 HISTOLDEHYD-RXN< group3 IMIDPHOSDEHYD-RXN> group4 HISTIDPHOS-RXN> group4 IMIDPHOSDEHYD-RXN< group4 HISTIDPHOS-RXN< group4