By addition of pH2, phosphoenolpyruvate (PEP) is converted to PLAC (a). By means of the PH-INEPT+ pulse sequence23, spin order is transferred to 13C (b). In a simplified model, PLAC is a 4-spin system composed of two weakly coupled protons, one 13 C nucleus, and one 31P nucleus (blue) with the corresponding J-couplings J12 = 6.90 Hz, J13 = 4.07 Hz, J23 = 3.80 Hz, J34 = 6.52 Hz, and J24 = 8.60 Hz.31 The sequence consists of two free evolution intervals and 1H/13 C RF pulses. Black bars denote 180° spin echo pulses.