Enzymatic Assay: The SCD1 enzymatic assay was done in a volume of 50 μL using 10 μg of RLM (prepared as described above) in a 96-well polypropylene plate (enzyme reaction buffer contains 0.1 M K-Phosphate Buffer, 10 mM ATP, 6 mM MgCl2. 1 mM CoA, 1 mM β-NADH, 1.6 mM L-glutathione, 20 μM Stearoyl-CoA). Stearoyl-[9,10-3H]-CoA (ARC-0390, 1 mCi/mL, 60 Ci/mmol,) was added at a final concentration of 2 μCi/mL. Test compound was then added to the reaction mixture at the selected concentration. After incubation at room temperature for 2 hours, 5 μL 1 N HCl was added to stop the reaction, followed by addition of 25 μL of 10% charcoal. The reaction mixture was then transferred to 96-well Multiscreen plate (Millipore, Cat#MSFCN6B50). [3H2O] was collected into Opti-plate (PE, Cat#6005290) by centrifuge, at 1,000 rpm for 2 minutes. 150 μL Microscint 40 (PE, cat #6013641) was then added to each well and counted on Topcount for [3H] counts per minute (cpm).
Enzyme Inhibition Assay: Human SCD-1 enzyme activity using HepG2 cell microsomes after treating with inhibitory compounds (% inhibition):Human hepatocarcinoma HepG2 cells (ATCC, HB-8065) are cultured to confluence and trypsinised. The cell pellet is taken up with 10 mM Tris (pH 7.4) sucrose (250 mM) DTT (1 mM) buffer and the cells are lysed by sonication. The microsomes are obtained after centrifugation at 10,000 g for 20 minutes at 4 C. followed by centrifugation of the supernatant at 100,000 g for 60 minutes at 4 C. The pellet is taken up with 10 mM Tris (pH 7.4) sucrose (250 mM) buffer at 4 C. and the microsomal proteins are assayed and stored at -196 C. (liquid nitrogen).The enzyme reaction measures the conversion of stearic acid (C18:0 fatty acid) to oleic acid (C18:1 fatty acid) by SCD-1. The enzyme reaction is started by adding 125 ug of HepG2 cell microsomal fraction to tubes (total reaction volume of 500 ul) containing 62 uM of stearic acid.
Inhibition of Scd1 in human HEK293A cell microsomes assessed as conversion of [14C]stearate to [14C]oleate pretreated for 10 mins measured after 60 mins
Inhibition of SCD1 in human HepG2 cells assessed as [14C]stearic acid to [14C]oleic acid conversion pretreated 15 mins before [14C]stearic acid addition measured after 4 hrs by HPLC based scintillation assay