Cystathionine β-lyase is a pyridoxal 5′-phosphate (PLP)-dependent enzyme that cleaves the Cβ-Sγ bond of cystathionine to convert L-cysteine into L-homocysteine. Cystathionine β-lyase is involved in the de novo synthesis of methionine in microorganisms and plants and plays an important role in bacterial virulence.

Method:
Cystathionine β-lyase (25 nM) catalyzed the conversion of L-(+)-cystathionine (100 μM) to homocysteine within 10 minutes. The formation of homocysteine was detected by measuring free thiols using 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB) at an absorbance of 412 nm.

Result:
Cystathionine β-lyase efficiently catalyzed the formation of homocysteine from L-(+)-cystathionine. The Resulting free thiols were significantly detected by DTNB-based colorimetric assay at 412 nm, indicating good enzymatic activity.[1]