Uronema marinum: identification and biochemical characterization of phosphatidylcholine-hydrolyzing phospholipase C.
Phosphatidylcholine (PC)-specific phospholipase D (PC-PLD) and phosphatidylcholine (PC)-specific phospholipase C (PC-PLC) activities have been detected in Uronema marinum. Partial purification of PC-PLC revealed that two distinct forms of PC-PLC (named as mPC-PLC and cPC-PLC) were existed in membrane and cytosol fractions. The two PC-PLC enzymes showed the preferential hydrolyzing activity for PC with specific activity of 50.4 for mPC-PLC and 28.3 pmol/min/mg for cPC-PLC, but did not hydrolyze phosphatidylinositol or phosphatidylethanolamine. However, the biochemical characteristics and physiological roles of both enzymes were somewhat different. mPC-PLC had a pH optimum in the acidic region at around, pH 6.0, and required approximately 0.4 mM Ca2+ and 2.5 mM Mg2+ for maximal activity. cPC-PLC had a pH optimum in the neutral region at around, pH 7.0, and required 1.6 mM Ca2+ and 2.5 mM Mg2+ for maximal activity. cPC-PLC, but not mPC-PLC, showed a dose-dependent inhibitory effect on the luminal-enhanced chemiluminescence (CL) responses and the viability of zymosan-stimulated phagocytes of olive flounder, indicating that cPC-PLC may contribute to the parasite evasion against the host immune response. Our results suggest that U. marinum contains PC-PLD as well as two enzymatically distinct PC-PLC enzymes, and that mPC-PLC may play a role in the intercellular multiplication of U. marinum and cPC-PLC acts as a virulence factor, serving to actively disrupt the host defense mechanisms.
Seo
Jung Soo
JS
Department of Aquatic Life Medicine, Pukyong National University, Busan 608-737, Republic of Korea.
Kim
Moo Sang
MS
Lee
Sang Hwan
SH
Kim
Ki Hong
KH
Lee
Hyung Ho
HH
Jeong
Hyun Do
HD
Chung
Joon Ki
JK
D000818:Animals; D002470:Cell Survival / Q000276:immunology; D016770:Ciliophora Infections / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D004306:Dose-Response Relationship, Immunologic; D005393:Fish Diseases / Q000276:immunology / Q000469:parasitology*; D005432:Flounder / Q000276:immunology / Q000469:parasitology*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008163:Luminescent Measurements / Q000662:veterinary; D016802:Oligohymenophorea / Q000201:enzymology* / Q000276:immunology; D010586:Phagocytes / Q000166:cytology / Q000276:immunology; D010713:Phosphatidylcholines / Q000378:metabolism; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
D010713:Phosphatidylcholines; D010738:Type C Phospholipases; C105598:phosphatidylcholine-specific phospholipase C