ISSN:
1573-4919
Keywords:
phospholipase D
;
hydrolysis
;
transphosphatidylation
;
sarcolemma
;
sarcoplasmic reticulum
;
heart
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract Myocardial phospholipase D (PLD) is located in different subcellular membranes, including sarcolemma (SL) and sarcoplasmic reticulum (SR). In this study, the kinetics of PLD-dependent hydrolytic and transphosphatidylation activities were examined in SL and SR fractions isolated from rat heart by measuring the formation of phosphatidic acid and phosphatidylethanol, respectively. The results showed that, compared to SR PLD, SL PLD had a higher Vmax, i.e. 373 vs. 70 nmol/mg protein/h for the hydrolytic activity and 415 vs. 60 nmol/mg protein/h for the transphosphatidylation activity. In comparison with the SR enzyme, SL PLD had a lower Km value for the hydrolytic activity (0.46 vs. 0.65 mM), but a higher Km for the transphosphatidylation activity (225 vs. 179 mM). These distinctive kinetic parameters suggest that SL PLD and SR PLD may be isoforms of the enzyme and/or have different membrane domain. Therefore, SL- and SR-localized PLD activities may be under independent control mechanism(s) and play distinct roles in normal conditions and pathological processes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00240035
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