Lysine acetylation is controlled by the balance of lysine acetyltransferase (KAT) activity, which transfer an acetyl group from acetyl-CoA to lysine on substrate proteins, and lysine deacetylase (KDAC) activity, which remove the acetyl groups. Many cancerous cells have been shown to have altered protein acetylation. One way to target this aberrant acetylation would be to target KATs. However, the specific substrates of each KAT are for the most part still unknown. I developed a protocol to determine the substrates of p300 using both high throughput and mass spectrometry approaches. For in vitro analysis, we performed acetylation assays with an acetyl-CoA analogue, 4 pentynoyl CoA, which carries an alkyne. For in vivo analysis, A549 cells were treated with sodium pentynoate prior to lysis. Click chemistry was used to conjugate either an azide dye or biotin azide to pentynoylated proteins for analysis via in-gel fluorescence or mass spectrometry. To account for non-specific utilization of 4-pentynoyl-CoA by other KATs, we compared substrates in the presence and absence of the p300 specific inhibitor, C646. Recent research has shown some brain cancer cell lines (U87, LN18, and T89) display decreased viability and increased phosphotyrosine levels when starved of glucose, while others display neither of these changes (LN229). I first confirmed the changes in viability and tyrosine phosphorylation in U87 and LN229 cells upon glucose deprivation and then determined the effect of deprivation on lysine acetylation.