Heterologous expression of leader-less pga gene in Pichia pastoris: intracellular production of prokaryotic enzyme

Heterologous expression of recombinant urate oxidase using the intein-mediated protein purification in Pichia pastoris

The potential of urate oxidase (uricase) for clinical use has been highlighted because of its role in lowering the blood uric acid levels for the treatment of tumor lysis syndrome. In the present study, the codon-optimized synthetic gene of Aspergillus flavus uricase was fused to the Mxe GyrA intein and chitin-binding domain. The construct was inserted into pPICZA and pPICZαA vectors and electroporated into Pichia pastoris GS115 for the cytosolic and secretory expression. Transformants were screened on gradients of Zeocin up to 2000 μg/ml to find multi-copy integrants. For both constructs, colonies with more resistance were screened for the highest uricase producers by enzyme assay. PCR analysis confirmed successful cassettes insertion into the genome and Mut + phenotype. The gene copy index was determined to be two and five for cytosolic and secretory strains, respectively. Productivity of the cytosolic and secretory strains was found to be 0.74 and 0.001 U/ml culture media in order while the cytosolic recombinant enzyme accounted for about 6% of total proteins. One-step purification of the expressed uricase was done with the aid of the chitin affinity column, followed by DTT induction for intein on-column cleavage. The yield of 40.8 mg/L and K m of 0.22 mM was obtained for intracellular expression. It seems that the intracellular production of uricase can indeed serve as an effective alternative to secretory expression. Moreover, this is the first report considering cytosolic production of uricase using the intein-mediated protein purification in the methylotrophic yeast, P. pastoris.

Production and secretion dynamics of prokaryotic Penicillin G acylase in Pichia pastoris

To take full advantage of recombinant Pichia pastoris (Komagataella phaffii) as a production system for heterologous proteins, the complex protein secretory process should be understood and optimised by circumventing bottlenecks. Typically, little or no attention has been paid to the fate of newly synthesised protein inside the cell, or its passage through the secretory pathway, and only the secreted product is measured. However, the system’s productivity (i.e. specific production rate q_p), includes productivity of secreted (q_p,extra) plus intracellularly accumulated (q_p,intra) protein. In bioreactor cultivations with P. pastoris producing penicillin G acylase, we studied the dynamics of product formation, i.e. both the specific product secretion (q_p,extra) and product retention (q_p,intra) as functions of time, as well as the kinetics, i.e. productivity in relation to specific growth rate (μ). Within the time course, we distinguished (I) an initial phase with constant productivities, where the majority of product accumulated inside the cells, and q_p,extra, which depended on μ in a bell-shaped manner; (II) a transition phase, in which intracellular product accumulation reached a maximum and productivities (intracellular, extracellular, overall) were changing; (III) a new phase with constant productivities, where secretion prevailed over intracellular accumulation, q_p,extra was linearly related to μ and was up to three times higher than in initial phase (I), while q_p,intra decreased 4–6-fold. We show that stress caused by heterologous protein production induces cellular imbalance leading to a secretory bottleneck that ultimately reaches equilibrium. This understanding may help to develop cultivation strategies for improving protein secretion from P. pastoris.

Key Points • A novel concept for industrial bioprocess development. • A Relationship between biomass growth and product formation in P. pastoris. • A Three (3) phases of protein production/secretion controlled by the AOX1-promoter. • A Proof of concept in production of industrially relevant penicillin G acylase.

Potential of Pichia pastoris for the production of industrial penicillin G acylase

This study deals with the potential of Pichia pastoris X-33 for the production of penicillin G acylase (PGA^A) from Achromobacter sp. CCM 4824. Synthetic gene matching the codon usage of P. pastoris was designed for intracellular and secretion-based production strategies and cloned into vectors pPICZ and pPICZα under the control of AOX1 promoter. The simple method was developed to screen Pichia transformants with the intracellularly produced enzyme. The positive correlation between acylase production and pga gene dosage for both expression systems was demonstrated in small scale experiments. In fed-batch bioreactor cultures of X-33/PENS2, an extracellular expression system, total PGA^A expressed from five copies reached 14,880 U/L of an active enzyme after 142 h; however, 60% of this amount retained in the cytosol. The maximum PGA^A production of 31,000 U/L was achieved intracellularly from nine integrated gene copies of X-33/PINS2 after 90 h under methanol induction. The results indicate that in both expression systems the production level of PGA^A is similar but there is a limitation in secretion efficiency.

Cell-specific Profiling of Nascent Proteomes Using Orthogonal Enzyme-mediated Puromycin Incorporation

Translation regulation is a fundamental component of gene expression, allowing cells to respond rapidly to a variety of stimuli in the absence of new transcription. The lack of methods for profiling nascent proteomes in distinct cell populations in heterogeneous tissues has precluded an understanding of translational regulation in physiologically relevant contexts. Here, we describe a chemical genetic method that involves orthogonal enzyme-mediated incorporation of a clickable puromycin analogue into nascent polypeptides. Using this method, we show that we can label newly synthesized proteins in a cell-specific manner in cells grown in culture and in heterogeneous tissues. We also show that we can identify the nascent proteome in genetically targeted cell populations using affinity enrichment and tandem mass spectrometry. Our method has the potential to provide unprecedented insights into cell-specific translational regulation in heterogeneous tissues.

A Proposal for Six Sigma Integration for Large-Scale Production of Penicillin G and Subsequent Conversion to 6-APA

Six Sigma methodology has been successfully applied to daily operations by several leading global private firms including GE and Motorola, to leverage their net profits. Comparatively, limited studies have been conducted to find out whether this highly successful methodology can be applied to research and development (R&D). In the current study, we have reviewed and proposed a process for a probable integration of Six Sigma methodology to large-scale production of Penicillin G and its subsequent conversion to 6-aminopenicillanic acid (6-APA). It is anticipated that the important aspects of quality control and quality assurance will highly benefit from the integration of Six Sigma methodology in mass production of Penicillin G and/or its conversion to 6-APA.

Comparative performance of S-adenosyl-L-methionine biosynthesis and degradation in Pichia pastoris using different promoters and novel consumption inhibitors

The yeast Pichia pastoris is a widely used host for recombinant protein expression, and has recently been engineered for whole-cell biocatalysis. The inducible P(AOX) and constitutive P(GAP) promoters are commonly employed. In this study, the S-adenosyl-L-methionine (SAM) biosynthesis and degradation efficiency of two P. pastoris strains were compared, and novel inhibitors that suppress SAM degradation were characterized. The strains exhibited clear physiological differences. P(GAP)-Pichia showed higher transcription and activity of SAM synthetase, and the rapid cell growth led to higher levels of spermidine synthesis from SAM. In contrast, P(AOX)-Pichia synthesized higher levels of glutathione from SAM, and this strain responded to hydrogen peroxide formation during methanol utilization. Aristeromycin proved an efficient inhibitor of SAM degradation in P(AOX)-Pichia; 0.02 mg/L led to a 36.36% reduction in the ratio of glutathionine:SAM, and SAM accumulation was enhanced by 7.74% to 11.83 g/L. Ethanol was an even more efficient inhibitor of SAM consumption in P(GAP)-Pichia; 8 g/L resulted in a 73.68% decrease in the ratio of SPD:SAM, and SAM production was elevated by 54.55% to 0.17 g/L/h.

Biotechnological advances on penicillin G acylase: pharmaceutical implications, unique expression mechanism and production strategies

In light of unrestricted use of first-generation penicillins, these antibiotics are now superseded by their semisynthetic counterparts for augmented antibiosis. Traditional penicillin chemistry involves the use of hazardous chemicals and harsh reaction conditions for the production of semisynthetic derivatives and, therefore, is being displaced by the biosynthetic platform using enzymatic transformations. Penicillin G acylase (PGA) is one of the most relevant and widely used biocatalysts for the industrial production of β-lactam semisynthetic antibiotics. Accordingly, considerable genetic and biochemical engineering strategies have been devoted towards PGA applications. This article provides a state-of-the-art review in recent biotechnological advances associated with PGA, particularly in the production technologies with an emphasis on using the Escherichia coli expression platform.