HYDROLYTIC SELECTIVITY OF PATATIN (LIPID ACYL HYDROLASE) FROM POTATO ( S O M U M TUBEROSUM L.) TUBERS TOWARD VARIOUS LIPIDS COREY ANDERSON, PRAPHAN PINSIRODOM and KIRK L. PARKIN' Department of Food Science I605 Linden Drive University of Wisconsin Madison, WI53706 Rcceived for Publication September 18,2000 Accepted for Publication May 4,2001 ABSTRACT The fatty acid and positional hydrolytic selectivity of lipid acyl hydrolase (UH; patatin) isolatedfi.ompotato tubers was determined for acylglycerol and phospholipid substrates. LAH was about 3-foM more selective for decanoyl residues over other acyl groups of 8-18 carbonsfor partial glyceride substrates. For both mono- and diacylglycerols, UHpreferred substrates with primary (sn- 1 (3)-) ester linkages, indicating a regiobias for these sites over sn-2-linked acyl groups. Similarly, hydrolytic activity on phospholipid substrates was 5- to IO- fold faster on sn-1-palmitoyl. sn-2-lysophospholipids than on intact phospho- lipids, indicating a preference for either lysophospholipids or sn-1-acyl sites, or both. LAH activity on partial glycerides was not activated by CaC12 and had a greater temperatureoptimwnrelative toLAHactivity onphospholipid substrates. These differences are likely based on differences inforces and structural features conferring envme-substrate recognition for these substrates within a common active site. INTRODUCTION Patatin is the common name for immunologically identical isoforms of the major storage (g1yco)protein in potato (Sohum tuberosum L.) tuber, accounting for up to 40% of the total tuber protein (Racusen and Foote 1980; Rosahl et al. 1986; Hofgen and Willmitzer 1990). Patatin is a slightly acidic protein with a I Corresponding author: TEL: 608-263-201 1 ; FAX: 608-262-6872; E-mail: klparkm@facstaff.wisc.edu Journal of Food Biochemistry 26 (2002) 63-74. All Rights Reserved. Topyright 2002 by Food & Nutrition Press, Inc.. Trwnbull, Connecticut. 63