1. Department
of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K.
2. Department
of Clinical Chemistry, Free University of Amsterdam, De Boelelaan
1117, 1081 HV Amsterdam, NL
3. Laboratory for Clinical
Biochemistry and Metabolism, Department of General Pediatrics, University Medical Center Freiburg, 79106 Freiburg, Germany
4. Division of Physiology
and Metabolism, MRC National Institute for Medical Research, the Ridgeway, Mill Hill, London NW7 1AA, U.K.