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Product Quality and Process
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Other amino acid sequence variants may occur post-translationally. At a low frequency, the leader sequence that directs the nascent protein to translocate into the endoplasmic reticulum may not be cleaved, producing a variant. Many proteins have lysine or arginine in their C-terminus. The basic amino acids in the C-terminus are liable to cleavage by carboxypeptidase. The cleavage of lysine at the C-terminus of the heavy chain of many IgG molecules by carboxypeptidase is often not complete, leaving some molecules with uncleaved C-terminus lysine.
Proteases in Leather Processing
Published in Devarajan Thangadurai, Jeyabalan Sangeetha, Industrial Biotechnology, 2017
Vasudeo P. Zambare, Smita S. Nilegaonkar
The carboxypeptidases act at C terminal of the polypeptide chain and liberate a single amino acid or a dipeptide. Carboxypeptidases can be divided into three major groups, serine carboxypeptidases, metallocarboxypeptidases, and cysteine carboxypeptidases, based on the nature of the amino acid residues at the active site of the enzymes. The enzymes can also hydrolyze the peptides in which the peptidyl group is replaced by a pteroyl moiety or by acyl groups.
Enzyme Catalysis
Published in Harvey W. Blanch, Douglas S. Clark, Biochemical Engineering, 1997
Harvey W. Blanch, Douglas S. Clark
In metalloenzymes a metal ion is present at the active site and this ion plays an important role in stabilizing negative charges that are formed in electrophilic catalysis. Zinc, copper and cobalt are commonly involved in coordination of oxyanions involved as reaction intermediates. The enzyme carboxypeptidase-A, which is a carboxyl-terminus exopeptidase (i.e., it acts by hydrolyzing the peptide from the carboxylic acid terminus), contains Zn2+ which polarizes the carbonyl oxygen of the terminal peptide bond. The terminal carboxylate is charge paired with the guanidinium cation of Arg145, leading to polarization of the terminal carboxylic carbonyl group. This polarization increases the electrophilicity of the carbonyl carbon and facilitates nucleophile-mediated hydrolysis of the amide bond. This is illustrated in the accompanying figure. In addition to stabilizing negative charges, metal ions serve as a source of potent nucleophilic hydroxyl ions. Metal-bound water molecules provide these nucleophilic hydroxyl groups at neutral pH.
A review on bio-functional models of catechol oxidase probed by less explored first row transition metals
Published in Journal of Coordination Chemistry, 2022
Rashmi Rekha Tripathy, Shuvendu Singha, Sohini Sarkar
Among all transition metal ions, zinc ion possesses much biological relevance in living systems. Important metalloenzymes, such as aminopeptidase, carboxypeptidase, alcohol dehydrogenase, and carbonic anhydrase, contain zinc(II) as cofactor which serves an essential role to activate catalytic features of them. All these enzymes play significant parts in cellular functions occurring in plants as well as in animal bodies. Designing new zinc(II) complexes to check their viability to biomimic active sites, which are present in different metalloenzymes, is an attractive field of modern research. Searching for new functional models for catechol oxidase has raised interest in the research of bioinorganic chemistry. Zinc(II)-complexes have been found to be capable of catechol oxidase activity. Although it is believed that the redox innocent nature of zinc cannot permit metal centric oxidation of catechols, quite satisfactory turnover numbers obtained for some of the zinc(II)-complexes confirm ligand centric mechanism like nickel(II).
Analysis of polysaccharide hydrolases secreted by Aspergillus flavipes FP-500 on corn cobs and wheat bran as complex carbon sources
Published in Preparative Biochemistry & Biotechnology, 2020
Lizzete Ruth Torres-Barajas, María Teresa Alvarez-Zúñiga, Guillermo Mendoza-Hernández, Guillermo Aguilar-Osorio
This group is composed by proteases and peptidases, like, carboxypeptidase, aminopeptidase, autophagic serine protease, aspergillopepsin, among others, which represent 12 and 10% of total proteins produced by A. flavipes FP-500 on CC and WB, respectively (Figure 3a,b). It has been reported that aspergillopepsin A is associated with the mechanism of cell wall fragmentation and endogenous recycling of cytoplasmic content in the hyphae. It is the second most abundant protease secreted during growth in limiting carbon source cultures.[64] Aspergillopepsin was found in both carbon sources. Other proteases like tripeptidyl peptidases have been identified as primarily responsible for the hydrolysis during the expression of heterologous proteins.[65] Serin-carboxy peptidases acts in the conidial formation and normal growth of the hyphae, as it has been observed in A. oryzae.[66] As can be seen, the presence of proteases has been reported in other Aspergillus species.
Kinetics of enzymatic reactions in the production of fish protein hydrolysates
Published in Journal of Dispersion Science and Technology, 2018
V. Yu. Novikov, S. R. Derkach, Yu. A. Kuchina, A. Yu. Shironina, V. A. Mukhin
It should be noted that some simplifications were introduced in the development of the model for the enzymatic hydrolysis of fish proteins. First, the mechanism takes into account the presence of only two fractions of proteins with different susceptibilities to the action of the enzyme, however it is possible that there are more two fractions. Secondly, the model does not take into account the complex composition of the enzyme itself, which contains several different molecules (enzymes) with different proteolytic activity and substrate specificity (e.g., trypsin, carboxypeptidase,[262728] acid proteinase,[9] and inactive protein). Finally, the model does not take into account thermal deactivation of the enzyme specimen and the chemical hydrolysis of proteins and other processes that can lead both to acceleration and deceleration of the rate of hydrolysis.