Inhibiting SHP2 in turn inhibited Ras dephosphorylation. Initially, cortical inhibitory pathways are selectively inhibited, causing symptoms of neuronal excitation. Endogenous nitrosamine formation can be inhibited by ascorbic acid. The activity of proteases is inhibited by protease inhibitors. It is allosterically stimulated by NADP and strongly inhibited by NADPH. However, when Beclin1 was overexpressed, tumor development was inhibited. Glutamine synthase activity is also inhibited via adenylation. For experimental purposes, SERCA can be inhibited by thapsigargin and induced by istaroxime. By example, when the triceps brachii is stimulated, the biceps is reflexively inhibited. Thus, glycolysis is inhibited in the liver but unaffected in muscle when fasting. This pathway is not inhibited by acidosis as happens with glycolysis of glucose. MI-63 binds to MDM2, reactivating p53 in situations where p53's function has become inhibited. For example, enzymes in a metabolic pathway can be inhibited by downstream products. Tyrosine can also be inhibited at the transcriptional level by the TyrR repressor. This pathway will be inhibited by atropine.