Front Matter

tained PLA 2 immobilized onto Sepharose (Labeque et al., 1993). This approach is

based on the decrease of plasma cholesterol by degradation of phospholipids in low-

density lipoproteins (LDL). An advanced model of this reactor is the plasma separa-

tor reactor which combines plasma separation and enzymatic conversion of phos-

pholipids in LDL (Shefer et al., 1993). With the same aim of plasma clearance

from LDL particles, PLA 2 from cobra venom was also immobilized to chitosan

beads in a circulating packed-bed reactor (Chen and Chen, 1998).

12.5.3 Phospholipase C

Because of its high stereospecificity, PLC can be used to obtain enantiomerically

pure 1,2-diacyl glycerols (Anthonsen et al., 1999) by hydrolysis of corresponding

glycerophospholipids. These compounds are important in biomedical research be-

cause of their function in signal cascades. They can also serve as substrates for the

production of synthetic phospholipids with natural configuration. Furthermore, hy-

drolysis catalyzed by PLC can be applied for the resolution of racemic phospholipid

mixtures. Thus, PAF and other enantiomerically pure phospholipids were prepared

starting from 1-O-alkyl-2-acetyl-rac-glycerol or 1,2-diacyl-rac-glycerols. After che-

mical conversion into the phosphocholine derivatives and subsequent treatment with

PLC, the phospholipids with unnatural configuration are separated from 1-O-alkyl-

2-acetyl-sn-glycerol or the 1,2-diacyl-sn-glycerols (Ko ̈tting and Eibl, 1994).

The enzymatic cleavage of the phosphate ester bond between the glycerol moiety

and phosphocholine in glycerophospholipids by PLC may also be used in the pro-

duction of organic phosphates such as glycerol-3-phosphate or dihydroxyacetone

phosphate (D’Arrigo et al., 1995). Takami and Suzuki (1994) produced dihydroxy-

acetone phosphate by PLC-catalyzed cleavage of phosphatidyldihydroxyacetone,

obtained from PC by PLD (Table 3). The formation of 1,3-cyclic glycerophosphate

has been reported by the action of PLC fromBacillus cereuson phosphatidylglycerol

(Shinitzky et al., 1993).

A PLC-catalyzed transfer reaction was first described by Kanfer and Spielvogel

(1975), in which^14 C sphingomyelin was formed by the transfer of the phosphoryl-

choline moiety of PC toN-(^14 C)-oleoyl-sphingosine. A series of interesting transes-

terification reactions have recently been described by means of bacterial PI-PC.

Starting from inositol 1,2-cyclic phosphate, which was obtained by PI-PLC-cata-

lyzed cleavage from soybean phosphatidylinositol, diverseO-alkyl inositol 1-phos-

phates were synthesized (Figure 11). The type of alkyl moieties ranged from simple

methyl via mannityl to peptidyl groups (Bruzik et al., 1996).

Moreover, there are reports on the involvement of PLC in chemo-enzymatic multi-

step syntheses such as the synthesis of phosphatidylinositol bearing a polyunsatu-

rated acyl group, where PLC fromBacillus cereusis used to remove the phosphor-

ylcholine moiety from 2-docosahexaenoyl-1-stearoyl-sn-glycerophosphocholine be-

fore chemical phosphorylation and coupling withmyo-inositol (Baba et al., 1996).

12.5 Examples of application 241