Endoplasmic reticulum (ER)-membrane-bound lysine N- acetyltransferase catalyzing the N6-acetylation of lysine residues in the lumen of the ER in various proteins, including PROM1 and BACE1, using acetyl-CoA as acetyl donor (PubMed:19011241, PubMed:22267734, PubMed:24556617, PubMed:31945187). Thereby, may regulate apoptosis through the acetylation and the regulation of the expression of PROM1 (PubMed:24556617). Acetylates and stabilizes BACE1 immature protein, leading to increased steady-state levels in neurons. By acting on BACE1 expression, may regulate amyloid beta-peptide formation (PubMed:19011241, PubMed:22267734). N(6)-lysine acetylation in ER maintains protein homeostasis and regulates reticulophagy (By similarity). {ECO:0000250|UniProtKB:E0CYC6, ECO:0000269|PubMed:19011241, ECO:0000269|PubMed:22267734, ECO:0000269|PubMed:24556617, ECO:0000269|PubMed:31945187}. This is the function of NAT8B (N-acetyltransferase 8B (putative, gene/pseudogene), ENSG00000204872).