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. Author manuscript; available in PMC: 2012 Aug 28.
Published in final edited form as: Clin Chem. 2004 Aug 3;50(10):1785–1796. doi: 10.1373/clinchem.2004.035907

Fig. 1. Substrates, products, and internal standards for the five lysosomal enzyme assays.

Fig. 1

The masses of the products and internal standards are indicated. The ceramide products and internal standards ASM-P, ASM-IS, GALC-P, GALC-IS, ABG-P, and ABG-IS undergo CID to give the common imminium ion shown (m/z = 264). GLA-P, GLA-IS, GAA-P, and GAA-IS undergo neutral-loss CID to give four different secondary ammonium ions. Enzymatic reactions with DBS are shown by solid arrows, and CID is shown by dashed arrows.