TABLE 3

FROM:

Radiolabeled Cholinesterase Substrates:In Vitro Methods for Determining Structure-Activity Relationships and Identification of a Positron Emission Tomography Radiopharmaceutical for In Vivo Measurement of Butyrylcholinesterase Activity

Scott E Snyder, Neeraja Gunupudi, Phillip S Sherman, Elizabeth R Butch, Marc B Skaddan, Michael R Kilbourn, Robert A Koeppe and David E Kuhl

Table 3. BuChE-mediated cleavage rates for all ChE substrates

Substrate*	[BuChE] (U/mL)†	Rate (A/min/U/L)‡	Relative rate (nBMP = 100)§
ACh	2	-0.377 0.006
	10	-0.43 0.03	n.d.
BCh	1	-1.58 0.08
	2	-1.59 0.04	n.d.
AMP	20	(0)
	100	-0.0151 0.0004	33.4 0.9
PMP	20	-0.063 0.002	139 5
iBMP	20	(0)
	100	-0.0183 0.001	41 1
nBMP	20	-0.045 0.002	100 3
2MBMP	20	(0)
	100	-0.0115 0.0003	25.4 0.6
iVMP	20	(0)
	100	-0.0055 0.0005	12 1
nVMP	10	-0.086 0.003
	20	-0.088 0.002	196 6

^* Substrate abbreviations as per Table 1. Substrate concentration = 50 mg/mL.

^† Enzyme concentrations are indicated in enzymatic units per milliliter (U/mL).

^‡ Cleavage rates measured as A/min/U/L and expressed as mean SD for n 3 assays.

^§ Rates expressed relative to nBMP = 100.

 Change in absorbance at [BuChE] = 20 U/mL was below the assay accuracy limit of A = 0.05 within 120 minutes (Rappaport, 1959) or <0.004 A/min/U/L.