Purification to homogeneity and some properties of l-phenylalanine ammonia-lyase of irradiated mustard (Sinapis alba L.) cotyledons

The Arabidopsis phenylalanine ammonia lyase gene family: kinetic characterization of the four PAL isoforms

“…The temperature optima (46-48°C) obtained for each isoform were quite comparable to native PALs isolated from other Brassicaceae members, such as Brassica campestris and B. juncea (both 45°C; www.brenda.uni-koeln.de and references therein). The pH optima, however, ranged from 8.4 to 8.8 (AtPAL4) to 8.9 (AtPAL2) and to 9.2 (AtPAL1), these values being within the ranges known for PAL from Hordeum vulgare (Koukol and Conn, 1961), Sinapis alba (Gupta and Acton, 1979) and Petroselinum crispum (Appert et al, 1994), respectively. Additionally, although AtPAL3 had a similar pH optimum (8.7-8.9), its temperature optimum (31°C ) was lower than that of the other isoforms, an observation which might possibly result from interference by the attached N-terminal His 6 -tag with packing of the native tetramer form.…”

The essential tyrosine‐containing loop conformation and the role of the C‐terminal multi‐helix region in eukaryotic phenylalanine ammonia‐lyases

“…On the other hand, PAL from fungi Ustilago hordei [70], Rhodotorula glutinis [55], Sporobolomyces pararoseus [71] or bacteria Streptomyces maritimus [5], S. verticillatus [7] obeyed the classical Michaelis–Menten kinetics. PAL isolated from far‐red irradiated mustard ( Sinapis alba L.) cotyledons exhibited also normal Michaelis–Menten kinetics [72]. Moreover, negative cooperativity has never been published for HAL enzymes, e.g.…”

“…In mustard, however, there is a pool of inactive enzyme which is activated by illumination [65]. The active PAL isolated from irradiated mustard cotyledons had a homotetrameric structure composed from 55 kDa subunits [72], which implies that this stable form contains no significant extensions to the HAL ⁄ PAL motif.…”

Phytoalexins: Enzymology and Molecular Biology

“…Exceptions to this include the enzyme from mustard cotyledons, which is composed of four 55,000 molecular weight subunits (78), and the enzyme from wheat leaves, reported to consist of two subunits of molecular weight 75,000 and two of 85,000 (79). PAL possesses two functionally active sites per tetramer (go), and, like histidine ammonia-lyase, the active sites contain a dehydroalanine residue (81 -83).…”