Differential phospholipid-labeling suggests two subtypes of phospholipase D in rat Leydig cells.
The aim of the present study was to compare the transphosphatidylation activity of phospholipase D (PLD) under different substrate labeling conditions, in order to investigate whether PLD in rat Leydig cells exhibited any substrate preferences for the alkyl- or acyl-form of phosphatidylcholine (PtdCho). The [3H]phosphatidylethanol formation in response to 4 beta-phorbol 12-myristate 13-acetate (PMA), sphingosine, or Ca(++)-ionophore A23187, was lower when Leydig cells were labeled with 1-O-[3H]alkyl lysoPtdCho compared with the responses when [3H]myristic acid was employed. In contrast, the results for the receptor agonists (vasopressin, bradykinin, and lysophosphatidic acid), using the two labels, showed more consistency. Thus, the PLD-activity induced by PMA, sphingosine, or A23187 has a more selective substrate range (i.e. mainly acyl-linked PtdCho) than the PLD-activity stimulated via a receptor. Our data suggests the existence of PLD isozymes that differ with respect to substrate specificity and activation mechanisms.
Lauritzen
L
L
Department of Biological Sciences, Royal Danish School of Pharmacy, Copenhagen O, Denmark.
Hansen
H S
HS
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007985:Leydig Cells / Q000201:enzymology*; D008297:Male; D010703:Phorbol Esters / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013110:Sphingosine / Q000494:pharmacology; D013379:Substrate Specificity
D010703:Phorbol Esters; D010743:Phospholipids; D000001:Calcimycin; D010739:Phospholipase D; D013110:Sphingosine