title: Enzyme and acid deconjugation of plasma sulfated metanephrines.
abstract: BACKGROUND
  Total (i.e. free+sulfated) metanephrines in plasma is a biomarker for the diagnosis of pheochromocytoma/paraganglioma. Sulfated metanephrines must be completely deconjugated by perchloric acid hydrolysis or sulfatase treatment prior to analytical measurement to enable quantification by current techniques. In this report, we compare the yield and efficiency of both methods.
  
  
  METHODS
  The deconjugation rate of synthetic sulfated metanephrines (normetanephrine (S-NMN), metanephrine (S-MN) and methoxytyramine (S-MT)) spiked in charcoal-stripped plasma was determined by boiling perchloric acid and compared to sulfatase treatment. Total plasma metanephrines (MN, NMN and MT) were also determined in patient samples by both methods.
  
  
  RESULTS
  The complete deconjugation of sulfated metanephrines is achieved after 30 min incubation with 0.1M boiling perchloric acid or upon sulfatase treatment. Ten minutes of acid hydrolysis (gold-standard) leads to a 30% underestimation of metanephrine concentrations. The enzyme hydrolysis is time and amount of sulfatase dependent. The rate of hydrolysis is analyte-dependent (MT>>NMN>MN), although it must contain at least 0.8 U/ml of sample. The Deming regression curves comparing acid versus enzyme hydrolysis on patient samples assessed that both methods gave similar unbiased concentrations.
  
  
  CONCLUSIONS
  Enzyme and acid treatments are equivalent and efficient for removing sulfate from metanephrines as long as the optimal protocol is used for each method. However, the gold standard method for acid hydrolysis at 10 min established more than 20 years ago was not satisfactory regarding the hydrolysis of metanephrines in plasma.
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Melanie
authors.initials: M
authors.lastname: Glauser
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Metrailler
authors.affiliation: Institute of Chemistry and Chemical Engineering, Ecole Polytechnique Fédérale de Lausanne, Batochime (Bat BCH), CH-1015 Lausanne, Switzerland.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Gerber-Lemaire
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Catherine
authors.initials: C
authors.lastname: Centeno
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Seghezzi
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Marielle
authors.initials: M
authors.lastname: Dunand
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Karim
authors.initials: K
authors.lastname: Abid
authors.affiliation: Centre Hospitalier Universitaire Vaudois, Service de Biomédecine, Hôpital Beaumont, Av de Beaumont 29, CH-1011 Lausanne, Switzerland.
authors.forename: Adeline
authors.initials: A
authors.lastname: Herren
authors.affiliation: Service de Biomédecine, Centre Hospitalier Universitaire Vaudois, Hôpital Nestlé 5th floor, office 5017, Av Pierre Decker, 1011 Lausanne, CH-1011 Lausanne, Switzerland. Electronic address: Eric.Grouzmann@chuv.ch.
authors.forename: Eric
authors.initials: E
authors.lastname: Grouzmann
mesh_terms: D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D008676:Metanephrine / Q000097:blood* / Q000737:chemistry* / Q000378:metabolism; D010472:Perchlorates / Q000737:chemistry* / Q000494:pharmacology; D013429:Sulfatases / Q000378:metabolism*
chemical_list: D010472:Perchlorates; D008676:Metanephrine; D013429:Sulfatases; C576518:Perchloric Acid
keywords: Desulfonation; Metanephrines; Sulfatase