$I.$ They activate many enzymes
$II.$ They participate in the oxidation of glucose to produce $ATP$
$III.$ Along with sodium ions, they are responsible for the transmission of nerve signals
Asn - Ser $+\,\underset{(excess)}{\mathop{{{(C{{H}_{3}}CO)}_{2}}O}}\,\xrightarrow{NE{{t}_{3}}}P$