Finally, the addition of Phe or t-CA to the formulation allows for a stable drug product with a long shelf-life

Finally, the addition of Phe or t-CA to the formulation allows for a stable drug product with a long shelf-life. this end, new PEGylation methodologies were developed, combined with testing PALs from different species as well as mutagenesis strategies to enhance PEG coverage and reduce the antigenicity of PAL [27, 29, 30]. Although most of the PAL enzymes explored as potential anti-cancer or PKU therapeutics were of yeast origin, PALs are also expressed in plants and bacteria. Early in the therapeutic research and development process, PAL from ((((characterization of PEGylated rstrains BLR or BL21(DE3) (EMD Millipore, Billerica, MA) (revaluation of PEGylated PALs Efficacy was assessed in BTBR was also greater than both refficacy In Sarkissian et al., we compared the effects of PEGylated recombinant efficacy of PEGylated r(p 0.002) (Fig 2B). rthat correlates with levels of PEGylation. Thus, PEGylation serves to protect rafter PEGylation, and it is challenging to identify specific properties that yielded such a superior response in the PKU mouse model. The N-terminal 54 amino acid extension and a 122 amino acid insertion conserved among plant and yeast PALs, but absent in bacterial PALs, was thought to be highly Rimantadine Hydrochloride immunogenic [27, 29, 32, 40]. Extensive mutagenesis of these domains in r em Rt /em PAL to reduce immunogenicity or by increasing PEG coverage was ineffective at reducing r em Rt /em PAL-PEG immunogenicity or improving efficacy [30]. em Np /em PAL and em Av /em PAL lack these domains, and one can speculate that this contributes to the superiority of the cyanobacterial PALs to em Rt /em PAL in reducing Phe levels in PKU mice when PEGylated. A robust PEGylation strategy to minimize or deflect an immune response, while keeping full enzyme activity was developed. Although only small variations in PEGylation levels were observed in the detectable reactive Rimantadine Hydrochloride sites when r em Av /em PAL was PEGylated at a percentage of 1 1:1.6, 1:2.4, or 1:3, there was an observable difference in effectiveness and immune response, highlighting the correlation of PEG protection with efficacy. It should be noted that many efforts were made to enhance PEG protection on r em Rt /em PAL, but r em Rt /em PAL-PEG by no means acquired the same effectiveness as r em Av /em PAL-PEG even with enhanced PEG protection through lysine improvements [25, 27, 29, 30]. As was similarly observed by Ikeda with r em Personal computer /em PAL, extensive PEGylation negatively affected enzyme activity in both r em Rt /em PAL-PEG and r em Np /em PAL-PEG having a reproducible 66% activity loss [26]. Remarkably, r em Av /em PAL activity was not reduced upon PEGylation. It was observed that r em Av /em PAL, and not r em Rt /em PAL nor r em Np /em PAL, experienced connected t-CA upon purification as observed in the crystal constructions and by reverse phase HPLC [32, 40, 41]. As the occupancy of the active site by t-CA stabilized r em Av /em PAL activity and discussed below, the absence of bound t-CA in r em Rt /em PAL and r em Np /em PAL might have made these enzymes Rimantadine Hydrochloride more susceptible to activity loss during the PEGylation reaction. PAL catalyzes the -removal of ammonia from Phe through an electrophilic assault of the Rabbit Polyclonal to SLC39A1 aromatic ring from the MIO prosthetic group (3,5-dihydro-5-methyldiene-4H-imidazol-4-one) in the PAL active site inside a Friedel-Crafts-type reaction [41C43]. The MIO in PAL is definitely highly susceptible to peptide fragmentation by reactive oxygen varieties (Erno Pungor, personal communication). To enhance long-term stability, safety of the MIO by binding PAL substrate or product was explored. It had been demonstrated that Phe and t-CA, but not tyrosine could enhance the Rimantadine Hydrochloride thermo-stability of r em Av /em PAL [32]. The loss of activity was identified as an instability of the active site MIO prosthetic group in which hydrolysis led to an irreversible clipping of the protein and was safeguarded by both Phe and t-CA (Dan Wendt and Erno Pungor, personal communication). As formulation excipients, both Phe and t-CA significantly stabilized r em Av /em PAL-PEG activity, extending its T90 activity stability from 11 to 75 weeks at 4C. As PAL catalyzed the conversion of Phe to t-CA, it is believed that t-CA remains in the active site until displaced by a new Phe molecule [32, 42]. In the absence of additional Rimantadine Hydrochloride Phe, two of the four active sites of r em Av /em PAL are occupied with t-CA [32]. In the presence of Phe, the percentage of t-CA.