Identification of beta-trace as prostaglandin D synthase

Area of Science:

• Biochemistry
• Neuroscience
• Enzymology

Background:

• Prostaglandin (PG) D synthase is a key enzyme in sleep regulation.
• Human cerebrospinal fluid (CSF) exhibits high PG D synthase activity, significantly exceeding that of rat brain homogenates.
• PGD synthase plays a critical role in physiological processes, including sleep.

Purpose of the Study:

• To purify and characterize prostaglandin (PG) D synthase from human cerebrospinal fluid (CSF).
• To investigate the structural and enzymatic relationship between human CSF PGD synthase and beta-trace, a major CSF protein.
• To confirm the identity of beta-trace as PGD synthase.

Main Methods:

• Purification of PGD synthase from human CSF using ammonium sulfate fractionation and column chromatographies (phenyl-Sepharose, DEAE-cellulose).
• Enzymatic characterization of the purified enzyme, including specific activity, optimum pH, Km, and SH requirement.
• Immunological cross-reactivity assays using antibodies against rat brain PGD synthase and human beta-trace.
• N-terminal amino acid sequencing of human PGD synthase, beta-trace, and purified PGD synthase.

Main Results:

• PGD synthase was purified approximately 8-fold from human CSF with a yield of 6%.
• The purified enzyme exhibited enzymatic properties similar to rat brain PGD synthase.
• Both purified PGD synthase and beta-trace cross-reacted with antibodies against each other and rat brain PGD synthase.
• N-terminal sequencing confirmed the identity of human PGD synthase, beta-trace, and purified PGD synthase.

Conclusions:

• Human beta-trace is structurally and enzymologically identical to prostaglandin (PG) D synthase.
• This finding clarifies the identity of a major CSF protein and its role in PGD synthesis.
• The high activity of PGD synthase in CSF suggests a significant role in central nervous system functions, potentially including sleep regulation.