analogs of l-carnitine containing a quarternary ammonium group were found to inhibit uptake ( d-carnitine , ki = 400 micron ; gamma-butyrobetaine , ki = 60 micron , choline chloride , ki = 14 mm ) , while those not containing this functional group ( gamma-aminobutyrate , d , l-beta-hydroxybutyrate ) had no significant effect at concentrations 100 times the apparent km of l-carnitine .
C2917324
analogs
C0007258
carnitine