title: Seasonal variation of tyrosinase activity in serum.
abstract: Serum samples for the analysis of tyrosinase activity were obtained from 10 healthy subjects in autumn, winter and summer. Tyrosinase was purified from 100 microl serum by adsorption to concanavalin A sepharose, the tyrosinase adsorbed to the gel being separated from other components by centrifugation. The gel was suspended in a buffer containing 5-hydroxy-indole-3-acetic acid as an antioxidant and incubated for 2 min with L-cysteine and D-L-dopa at 37 degrees C. The 5-S-L-cysteinyl-L-dopa formed was measured by HPLC and electrochemical detection. Tyrosinase has high stereo-specificity for the L-enantiomer of dopa, and correction for non-specific oxidation was made by simultaneous measurement of 5-S-L-cysteinyl-D-dopa formed from D-dopa. Whereas the oxidation of L-dopa catalysed by tyrosinase ws inhibited by L-tyrosine, the non-specific oxidation of D-dopa was not. Mean serum tyrosinase activity was 0.9 nkatal/l in summer, 0.8 nkatal/l in autumn and 0.4 nkatal/l in winter. The range of tyrosinase activity was much higher in summer and autumn than in winter.
authors.affiliation: Department of Dermatology, University of Lund, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Sonesson
authors.forename: S
authors.initials: S
authors.lastname: Eide
authors.forename: H
authors.initials: H
authors.lastname: Rorsman
authors.forename: E
authors.initials: E
authors.lastname: Rosengren
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007980:Levodopa / Q000737:chemistry; D008297:Male; D014442:Monophenol Monooxygenase / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D012621:Seasons
chemical_list: D007980:Levodopa; D014442:Monophenol Monooxygenase