Disease relevance of PLB2

• By incubation of phospholipase B1 and phospholipase B2 with endoglycosidase H from Streptomyces griseus, one main protein with an apparent Mr of 67 000 and the same residual carbohydrate content was obtained [1].

High impact information on PLB2

• Upon overexpression of PLB2 in a plb1 plb3 mutant background, phospholipase B activity was detectable in the plasma membrane, periplasmic space extracts and the culture supernatant [2].
• Deletion of Plb2p function had no effect on glycerophosphoinositol or glycerophosphocholine release in vivo, in contrast to a deletion of Plb3p function, which resulted in a 50% reduction of phosphatidylinositol breakdown and glycerophosphoinositol release from the cells [2].
• The PLB2 gene product shows lysophospholipase activity toward lysophosphatidylcholine, lysophosphatidylserine, and lysophosphatidylethanolamine [3].
• Moreover, overexpression of PLB2 was associated with saturation at a higher cell density, and an increase in total cellular phospholipid content, but no change in phospholipid composition or fatty acid incorporation into cellular lipids [3].
• This gene, which is located adjacent to the PLB1 gene on the left arm of chromosome XIII and which we refer to as PLB2, encodes a phospholipase B/lysophospholipase [3].

Biological context of PLB2

• PLB2 gene expression was found to be maximal during exponential growth conditions and was decreased in late phase, in a manner similar to other genes involved in phospholipid metabolism [3].

Anatomical context of PLB2

• Two forms of phospholipase B could be solubilized from the plasma membrane of Saccharomyces cerevisiae, separated by gel filtration with Sephacryl S-300 and identified by SDS-polyacrylamide gel electrophoresis as glycoproteins of the apparent molecular weights of about 220 000 (phospholipase B1) and 145 000 (phospholipase B2) [1].

Associations of PLB2 with chemical compounds

• Similar to Plb1p, Plb2p appears to accept all major phospholipid classes, with a preference for acidic phospholipids including phosphatidylinositol 3',4'-bisphosphate and phosphatidic acid [2].
• At the pH optimum of 2.5-3.5, the order of substrate preference of Plb1p and Plb2p is PtdSer (phosphatidylserine)>PtdIns>PtdCho (phosphatidylcholine>PtdEtn (phosphatidylethanolamine) [4].
• This effect is ascribed to the pH response of Plb1p, because Plb2p does not contribute to the degradation of PtdIns and PtdCho in vivo [4].

References