Phospholipase A2

I.U.B.: 3.1.1.4
Phosphatidylcholine 2-acetylhydrolase

Enzymatic Reaction (image will open in a new window) 

Phospholipase A2 represents a class of heat-stable, calcium-dependent enzymes catalyzing the hydrolysis of the 2-acyl bond of 3-n-phosphoglycerides. [This enzyme is named Phospholipase A2 to denote its 2-acyl specificity (Uthe 1971).]

Phospholipase A2 has been isolated from pancreas, snake and bee venoms. Forst et al. (1986), Chan et al. (1982), Coulard et al. (1987) and Horigome et al. (1987) report on platelet phospholipase A2. The primary structure of human pancreatic PLA2 has been reported by Verheij et al. (1983).

Phospholipases are involved in lipid metabolism and are important probes of structure-function relationships in biological membranes. Dawson 1973).

Characteristics of Phospholipase A2 from Crotalus adamanteus venom:

Two proteins (Aα, Aβ) exhibiting Phospholipase A activity have been isolated from this source. (Saito and Hanahan 1962, Wells and Hanahan 1969). Each protein is composed of dimeric subunits, Aα, Bβ, respectively (Wells 1971). The two proteins have similar activities but are chromatographically and electrophoretically distinct. Heinrikson et al. (1977) report on the distinctive structural features of the two enzymes and the complete amino acid sequence of phospholipase A2α.

Molecular weight: 30,000 (Wells 1969).

Extinction coefficient: = 22.7 (Wells 1969).

Isoelectric point: 4.55 and 4.40 for Aα and Aβ respectively (Saito 1962).

Activators: Calcium ion (Dennis 1973).

Inhibitors: Zinc, barium, and manganese ions (Uthe 1971). Also see Golec et al. (1992).

Specificity: Substrate specificity has been investigated (VanDeenen 1963).

Mechanism: A kinetic mechanism for this enzyme has been proposed (Wells 1972).

Stability: The enzyme is stable at 90°C and pH 3.0 for at least five minutes. (Uthe 1971; Saito 1962).