GCH1 and hypertensive disorder: (115) performed a control experiment—knockdown of the 26S proteasome regulatory subunit PA700 by siRNA and modifications of PA700 by tyrosine nitration in vitro—and the results indicated that PA700 nitration could promote the combination with the 20S proteasome, activate the 26S proteasome, and reduce GTPCH I and vascular protective enzyme BH4 expression, ultimately damaging endothelial cells in Ang II-induced hypertension.