Structural and phylogenetic comparison of three pepsinogens from Pacific bluefin tuna: molecular evolution of fish pepsinogens

The amino acid sequences of three pepsinogens (PG1, PG2 and PG3) of Pacific bluefin tuna (Thunnus orientalis) were deduced by cloning and nucleotide sequencing of the corresponding cDNAs. The amino acid sequences of the pre-forms of PG1, PG2 and PG3 were composed of a signal peptide (16 residues each), a propeptide (41, 37 and 35 residues, respectively) and a pepsin moiety (321, 323 and 332 residues, respectively). Amino acid sequence comparison and phylogenetic analysis indicated that PG1 and PG2 belong to the pepsinogen A family and PG3 to the pepsinogen C family. Homology modeling of the three-dimensional structure suggested that the remarkably high specific activity of PG2 toward hemoglobin, which had been found previously, was partly due to a characteristic deletion of several residues in the S1'-loop region that widens the space of the active site cleft region so as to accommodate protein and larger polypeptide substrates more efficiently. Including the tuna and all other fish pepsinogen sequences available to date, the molecular phylogenetic comparison was made with reference to evolution of fish pepsinogens. It was suggested that functional divergences of pepsinogens (pepsins) occurring in fishes as well as in mammals, correlated with differences in various aspects of fish physiology.     

Purification and characterization of pepsinogens from the gastric mucosa of African coelacanth, Latimeria chalumnae, and properties of the major pepsins

Two major pepsinogens, PG1 and PG2, and one minor pepsinogen, PG3, were purified from the gastric mucosa of African coelacanth, Latimeria chalumnae (Actinistia). PG1 and PG2 were much less acidic than PG3. Their molecular masses were estimated by SDS-PAGE to be 37.0, 37.0 and 39.3 kD, respectively. When incubated at pH 2.0, PG1 and PG2 were converted autocatalytically to the mature pepsins through an intermediate form, whereas PG3 was converted to an intermediate form, but not to the mature pepsin autocatalytically. The N-terminal sequencing indicated that the 42 residue sequences of the propeptides of PG1 and PG2 were essentially identical with each other, but different from that of PG3. A phylogenetic tree based on the N-terminal propeptide sequences indicates that PG1 and PG2 belong to the pepsinogen A group, and PG3 to the pepsinogen C group. From the phylogenetic comparison, coelacanth PG1 and PG2 appear to be evolutionally closer to tetrapod pepsinogens A than ray-finned fish pepsinogens A, consistent with the traditional systematics. Pepsins 1 and 2 were essentially identical with each other and rather similar to mammalian pepsins A in the pH optimum toward hemoglobin (pH 2-2.5), the cleavage specificity toward oxidized insulin B chain and strong inhibition by pepstatin, except that they possessed a significant level of activity in the higher pH range unlike mammalian pepsins A.     

Purification, characterization, and amino acid sequences of pepsinogens and pepsins from the esophageal mucosa of bullfrog (Rana catesbeiana)

Two pepsinogens (pepsinogens 1 and 2) were purified from the esophageal mucosa of the bullfrog (Rana catesbeiana), and their molecular weights were determined to be 40,100 and 39,200, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The NH2-terminal 70-residue sequences of both pepsinogens are the same, including the 36-residue activation segment. Furthermore, a cDNA clone encoding frog pepsinogen was obtained and sequenced, which permitted deduction of the complete amino acid sequence (368 residues) of one of the pepsinogen isozymogens. The calculated molecular weight of the protein (40,034) coincided well with the values obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results are incompatible with the previous report (Shugerman R. P., Hirschowitz, B. I., Bhown, A. S., Schrohenloher, R. E., and Spenney, J. G. (1982) J. Biol. Chem. 257, 795-798) that the major pepsinogen isolated from the bullfrog esophageal gland is a unique "mini" pepsinogen with a molecular weight of approximately 32,000-34,000. The two pepsinogens were immunologically indistinguishable from each other and related to human pepsinogen C. The deduced amino acid sequence was also more homologous with those of pepsinogens C than those of pepsinogens A and prochymosin. These results indicate that the frog pepsinogens belong to the pepsinogen C group. They were both glycoproteins, and therefore, this is the first finding of carbohydrate-containing pepsinogens C. Both pepsinogens were activated to pepsins in the same manner by an apparent one-step mechanism. The resulting pepsins were enzymatically indistinguishable from each other, and their properties resembled those of tuna pepsins.     

Purification and characterization of pepsinogens and pepsins from Asiatic black bear, and amino acid sequence determination of the NH2-terminal 60 residues of the major pepsinogen

Five pepsinogens were purified to homogeneity from the gastric mucosa of Asiatic black bear and termed pepsinogens I-1, I-2, II-1, II-2, and III. Pepsinogen II-1 was the major component and accounted for more than half of the total pepsinogens. Their molecular weights were estimated to be 40,000 for pepsinogens I-1 and I-2, 38,000 for pepsinogens II-1 and II-2, and 42,000 for pepsinogen III. They resembled each other in amino acid composition, except that pepsinogens I-1 and I-2 contained larger numbers of basic residues than the others. Pepsinogen III was a glycoprotein containing about 3.7% carbohydrate. Each was activated to the corresponding pepsin and their enzymatic characteristics were investigated. The optimal pH against hemoglobin was about 2.2 for pepsin I-1, and about 2.5 for pepsins II-1, II-2, and III. Each pepsin was inhibited by pepstatin as well as porcine pepsin and also by diazoacetyl-DL-norleucine methyl ester, 1,2-epoxy-3-(p-nitrophenoxy)-propane, and p-bromophenacyl bromide. Each pepsin could hydrolyze N-acetyl-L-phenylalanyl-3,5-diiodo-L-tyrosine, but the specific activity was much lower than that of porcine pepsin. Activation peptides corresponding to residues 1-43, 1-25, and 26-43 were isolated from an activation mixture of pepsinogen II-1. The amino acid sequences of these peptides and of the NH2-terminal portions of pepsinogen II-1 and pepsin II-1 were determined, resulting in the complete NH2-terminal 60-residue sequence of pepsinogen II-1.     

The pathway of pepsin-catalysed transpeptidation. Evidence for the reactive species being the anion of the acceptor molecule

Several minor pepsinogens, present in extracts of bovine fundic mucosa obtained from the fourth stomach or abomasum, were separated from the main pepsinogen by chromatography on hydroxyapatite at pH7.3. The major pepsinogen and two of these minor pepsinogens were studied in detail. All three zymogens have N-terminal Ser-Val-, C-terminal -Val-Ala and not more than 1mol of glucose/mol of protein; no significant differences in amino acid composition were found. The pepsinogens differ in their organic phosphate content, which accounts for their chromatographic separation. By activation at 0 degrees C and pH2, a corresponding series of pepsins is formed. These enzymes were separated by hydroxyapatite chromatography at pH5.7. All the pepsins have N-terminal valine, C-terminal alanine and are free from carbohydrate. Again the only difference detected among them is in their organic phosphate content. The pepsins of high phosphate content are converted by an acid phosphatase in vitro into pepsins of low phosphate content.     

Difference of activation processes and structure of activation peptides in human pepsinogens A and progastricsin

The activation processes of two human pepsinogens A (pepsinogens 3 and 5) and progastricsin were compared with special attention to pepsinogens 3 and 5. Each zymogen was converted to pepsin in a stepwise manner through intermediate forms. In pepsinogens A, the major cleavage site was the Leu23-Lys24 bond and this cleavage was suggested to occur intramolecularly. When each of the pepsins A was added to the corresponding pepsinogen A exogenously, the latter was rapidly converted to pepsin, releasing the 47-residue intact activation segment. In this case, the Leu47-Val48 bond connecting the activation segment with the pepsin moiety was cleaved by an intermolecular reaction. On the other hand, when the pepsinogen A-pepstatin complex was attacked by each corresponding pepsin A added exogenously, significant cleavage by an intermolecular reaction occurred at the Asp25-Phe26 bond, generating the Phe26-intermediate form. These shifts of the cleavage sites in pepsinogens A depending on the activation conditions are likely to correlate with the conformation of the activation segment. These results can be explained consistently in terms of a proposed molecular model of activation.     

Pepsinogens and pepsins from Japanese seabass (Lateolabrax japonicus)

Three pepsinogens (PG1, PG2, PG3) were highly purified from the stomach of Japanese seabass (Lateolabrax japonicus) by ammonium sulfate fractionation, DEAE-Sephacel anion exchange column chromatography and Sephacryl S-200 gel-filtration. Two dimensional polyacrylamide gel electrophoresis (2D-PAGE) analysis revealed that the molecular masses of the three PGs were 35, 37, and 34kDa, and their isoelectric points were 5.3, 5.1, and 4.7, respectively. Zymography analysis showed that the three pepsinogens had different mobilities and enzymatic activities under native conditions. Pepsinogens converted into their active form pepsins under pH 2.0 by one-step pathway or stepwise pathway. All three pepsins were completely inhibited by pepstatin A, a typical aspartic proteinase inhibitor. The N-terminal amino acid sequences of the three pepsinogens were determined to the 30th, 30th and 28th amino acid residue and those of their corresponding active form pepsins were also determined to the 19th, 18th and 20th amino acid residue, respectively. All amino acid sequences of Japanese seabass PGs revealed high identities to reported fish and mammalian pepsinogens. The effective digestion of fish and shrimp muscular proteins by pepsins indicated their physiological function in the degradation of food proteins.     

A comparative study on the NH2-terminal amino acid sequences and some other properties of six isozymic forms of human pepsinogens and pepsins

Six pepsinogen isozymogens, including five forms of pepsinogen A (PGA) and an apparently single form of pepsinogen C (PGC), were isolated simultaneously from the purified total pepsinogen fraction of human gastric mucosa by fast protein liquid chromatography on a Mono Q column, and their NH2-terminal amino acid sequences and some other properties were compared. Upon activation at pH 2.0, all the isozymogens were converted to the corresponding pepsins in a stepwise manner through intermediate forms. The activation rates and the cleavage sites in the activation peptide segment to generate intermediate forms were significantly different among the isozymogens. The NH2-terminal 85-residue amino acid sequences of these isozymogens were determined, including the sequences of the activation peptide segments and the NH2-terminal regions of the corresponding pepsins. Differences in amino acid sequence were found at positions 43 and 77 among the pepsinogen A isozymogens; the residue at position 43 was Lys in PGA-5, PGA-4, and PGA-3a, and Glu in PGA-3 and PGA-2, and the residue at position 77 was Leu in PGA-5 and PGA-4 and Val in PGA-3 and PGA-2. Phosphate was not found in any of the isozymogens. The corresponding pepsins also showed significant variations in properties such as specific activities toward synthetic and protein substrates, pH dependence of activity, susceptibility to various inhibitors, and thermal and alkaline stabilities.     

Purification and characterization of goat pepsinogens and pepsins

Three type-A and two type-C pepsinogens, namely, pepsinogens A-1, A-2, A-3, C-1, and C-2, were purified from adult goat abomasum. Their relative levels in abomasal mucosa were 27, 19, 14, 25, and 15%, respectively. Amino acid compositions were quite similar between isozymogens of respective types, but different between the two types especially in the Glx/Asx and Leu/Ile ratios. NH₂-terminal amino acid sequences of pepsinogens A-3 and C-2 were SFFKIPLVKKKSLRQNLIEN- and LVKIPLKKFKSIRETM-, respectively. Pepsins A and C showed maximal hemoglobin-digestive activity at around pH 2 and 3, respectively, and specific activities of pepsins C were higher than those of pepsins A. Two subtypes of pepsin A were obvious, namely pepsin A-2/3 which maintains its activity in the weakly acidic pH region over pH 3 and pepsin A-1, which does not. Hydrolysis of oxidized insulin B chain by goat pepsins A occurred primarily at Ala14-Leu15 and Leu15-Tyr16 bonds.     

Amphibian pepsinogens: purification and characterization of xenopus pepsinogens, and molecular cloning of Xenopus and bullfrog pepsinogens

Two pepsinogens (Pg C and Pg A) were isolated from the stomach of adult Xenopus laevis by Q-Sepharose, Sephadex G-75, and Mono-Q column chromatographies. Autolytic conversion and activation of the purified Pgs into the pepsins were examined by acid treatment. We determined the amino acid sequences from the NH2-termini of Pg C, pepsin C, Pg A, and pepsin A. Based on the sequences, the cDNAs for Pg C and Pg A were cloned from adult stomach RNA, and the complete amino acid sequences of the Pg C and Pg A were predicted. In addition, a Pg A cDNA was cloned from the stomach of adult bullfrog Rana catesbeiana, and the primary structure of the Pg A was predicted. Molecular phylogenetic analysis showed that such anuran Pg C and Pg A belong to the Pg C group and the Pg A group in vertebrates, respectively. The molecular properties of Pg C and Pg A, such as size, sequences of the activation peptide and active site, profile of autolytic activation, and pH dependency of proteolytic activity of the activated forms, pepsin C and pepsin A, resemble those of Pgs found in other vertebrates. However, the hemoglobin-hydrolyzing activity of Xenopus pepsin C is completely inhibited in the presence of equimolar pepstatin, an inhibitor of aspartic proteinases. Thus, the Xenopus pepsin C differs significantly from other vertebrate pepsins C in its high susceptibility to pepstatin, and closely resembles A-type pepsins.     

Pepsinogen C and pepsin C from gastric mucosa of Japanese monkey. Purification and characterization.

A new pepsinogen component, pepsinogen C, was purified from the gastric mucosa of Japanese monkey. The chromatographic behavior of this component on DE-32 cellulose was coincident with that of pepsinogen III-2 previously reported (1), and final purification was performed by large-scale polyacrylamide disc gel electrophoresis. The molecular weight was 35,000 as determined by gel filtration. The ratios of glutamic acid to aspartic acid and of leucine to isoleucine were higher than those of other Japanese monkey pepsinogens. The activated form, pepsin C, had a molecular weight of 27,000 and contained a large number of glutamic acid residues. The optimal pH for hemoglobin digestion was 3.0. Pepsin C could scarcely hydrolyze the synthetic substrate, N-acetyl-L-phenylalanyl-3, 5-diiodo-L-tyrosine (APDT). 1, 2-Epoxy-3-(p-nitrophenoxy)propane (EPNP), p-bromophenacyl bromide, and diazoacetyl-DL-norleucine methyl ester (DAN) inhibited pepsin C [EC 3.4.23.3] in the same way as pepsin III-3 of Japanese monkey. The susceptibility to pepstatin of pepsin C was lower than that of pepsin III-3, and 500 times more pepstatin was required for the same inhibitory effect. The classification and nomenclature of Japanese monkey pepsinogens and pepsins are discussed.     

Comparative pepstatin inhibition studies on individual human pepsins and pepsinogens 1,3 and 5(gastricsin) and pig pepsin A

Human gastric juice contains 3 major proteolytic components (pepsins1,3 and 5 or gastricsin). Pepsin 1 is increased in peptic ulcer and it's properties are relatively poorly understood. Studies with pepstatin the highly specific aspartic-protease inhibitor have therefore been carried out on individual active and proenzymes to assess any enzymic similarities. Human pepsin 1 was inhibited with high affinity similar to pepsin 3, whereas pepsin 5(gastricsin) was at least 40 times less sensitive. Inhibition of human pepsinogens 1,3 and 5 and pig pepsinogen A showed similar trends to the active enzymes. Studies using Sephadex gel filtration showed that pepstatin does not bind to pepsinogens and inhibition arises from pepstatin binding the pepsins released upon activation. Pepstatin inhibition was shown to be relatively independent of pH between 1.5 and 3.8 although at higher pH inhibition was less effective. The evidence suggests that pepsin 1 is similar to pepsin 3 and pepstatin inhibits by a one to one molecular binding to the active site. The explanation for the reduced affinity of pepstatin to pepsin 5(gastricsin) needs further study by co-crystallisation X-ray analysis.     

Biochemical and immunological characterizations of rat pepsinogens and pepsins

Biochemical and immunological properties of two kinds of pepsinogens isolated from the gastric mucosal extracts of adult Wistar rats were studied. Their activated enzymes were prepared from the zymogens using a DEAE-Sepharose CL-6B column. The isoelectric points of pepsinogens I and II were estimated to be 3.90 and 3.75, respectively, by isoelectric focusing, and those of pepsins I and II to be 3.60 and 3.45, respectively. Amino acid compositions of the two pepsinogens or pepsins were strikingly similar to each other and neither pepsinogen I nor II contained organic phosphate. The biochemical properties of rat preparations compared with porcine pepsinogens A and C and pepsins A [EC 3.4.23.1] and C [EC 3.4.23.3] showed that rat pepsinogens and pepsins resembled porcine pepsinogen C and pepsin C, respectively. Pepsinogens I and II were demonstrated to share a similar immunogenic molecular structure by double diffusion analysis and Laurell immunoelectrophoresis. Rabbit antipepsinogen I serum cross-reacted with the mouse preparation but did not with the rabbit and porcine preparations. The possibility of the genetically controlled occurrence of pepsinogens I and II in the rat is discussed.     

Comparative Pepstatin Inhibition Studies on Individual Human Pepsins and Pepsinogens 1,3 and 5(gastricsin) and Pig Pepsin A

Human gastric juice contains 3 major proteolytic components (pepsins1,3 and 5 or gastricsin). Pepsin 1 is increased in peptic ulcer and it's properties are relatively poorly understood. Studies with pepstatin the highly specific aspartic-protease inhibitor have therefore been carried out on individual active and proenzymes to assess any enzymic similarities. Human pepsin 1 was inhibited with high affinity similar to pepsin 3, whereas pepsin 5(gastricsin) was at least 40 times less sensitive. Inhibition of human pepsinogens 1,3 and 5 and pig pepsinogen A showed similar trends to the active enzymes. Studies using Sephadex gel filtration showed that pepstatin does not bind to pepsinogens and inhibition arises from pepstatin binding the pepsins released upon activation. Pepstatin inhibition was shown to be relatively independent of pH between 1.5 and 3.8 although at higher pH inhibition was less effective. The evidence suggests that pepsin 1 is similar to pepsin 3 and pepstatin inhibits by a one to one molecular binding to the active site. The explanation for the reduced affinity of pepstatin to pepsin 5(gastricsin) needs further study by co-crystallisation X-ray analysis.     

A pepsinogen from rainbow trout

1. A pepsinogen, Ia on the basis of its electrophoretic mobility, from rainbow trout stomach, has an optimum pH near 2 for activation. 2. The cognate pepsin is denatured at pH values above 7, in contrast to the zymogen, which is slightly more alkali-stable. It has an optimum pH of 3 for proteolysis of denatured hemoglobin. 3. The intrinsic reactivity of the zymogen and pepsin (rates of activation and of proteolysis, respectively) are quite high, but as they operate at the environmental temperature of the fish, are remarkably similar to rates of activation and proteolysis by mammalian pepsinogens and pepsins.     

Development-dependent expression of isozymogens of monkey pepsinogens and structural differences between them

The developmental changes in the expression of monkey pepsinogens and structural differences between the polypeptides were investigated. Monkey pepsinogens included five different components, namely, pepsinogens A-(1-4) and progastricsin. Their respective relative levels and specific activities changed significantly during development. The sequential expression of genes for type-A pepsinogens was particularly noteworthy. Pepsinogen A-3 was the major zymogen at the newborn stage, accounting for nearly half of the total pepsinogens at this stage. Pepsinogen A-2 became predominant at the 4-month stage, and pepsinogen A-1 predominated at the juvenile and adult stages. Enzymatic properties of pepsinogens A-1, A-2 and A-3 were similar but not identical to those of pepsinogen A-4 and progastricsin, in particular with respect to the activation processes. Each pepsin digested various protein substrates but some differences in specificity were evident. cDNA clones for five pepsinogens were isolated, and the nucleotide sequences were determined. Each cDNA contained leader, pro, and pepsin regions that encoded 15, 47, and 326 amino acid residues, respectively, with the exception of the cDNA for progastricsin in which the pro and pepsin regions encoded 43 and 329 amino acid residues, respectively. Type-A pepsinogens exhibited a high degree of similarity, with over 96% of bases in the nucleotide sequences of the protein-coding regions being identical. Northern analysis revealed that the level of expression of genes for type-A pepsinogens and for progastricsin was significant at the fetal stage and increased with development.     

Isolation and characterization of pepsinogen from Trimeresurus flavoviridis (Habu snake)

Pepsinogen was isolated from the gastric mucosa of Trimeresurus flavoviridis (Habu snake) by DEAE-cellulose and DEAE-Sepharose ion-exchange chromatographies, and Sephacryl S-200 gel-chromatography. The yield calculated from the crude extract was 29% with 6.2-fold purification. The purified pepsinogen gave a single band on both native- and SDS-PAGE. As no other active enzyme was detected on the chromatographies, it was concluded that the Habu snake has one major pepsinogen. The molecular mass of the pepsinogen was estimated to be 38 kDa by SDS-PAGE. The sequence of the N-terminal 26 amino acid residues was determined and compared with those of other pepsinogens. The N-terminal structure of Habu snake pepsinogen was more homologous with those of mammalian pepsinogens C than those of mammalian pepsinogens A. The pepsinogen was rapidly converted to pepsin by way of an intermediate form induced by acidification. The optimum pH of Habu snake pepsin for bovine hemoglobin was 1.5-2.0, and it retained full activity at pH 6.2 and 30 degrees C on incubation for 30 min. The optimum temperature for the snake pepsin was 50 degrees C and it was stable at 40 degrees C on incubation for 10 min. The proteolytic activity of the pepsin toward bovine hemoglobin was about two times higher than that of porcine pepsin A, however, the activity toward oxidized bovine insulin B-chain was lower than that of porcine pepsin A, and it did not hydrolyze oligopeptides. The specificity for oxidized bovine insulin B-chain of the pepsin was different from that of porcine pepsin A. Habu snake pepsin was inhibited by pepstatin A but not by serine, cysteine, or metallo protease inhibitors.     

Purificaton and characterization of a pepsinogen and its pepsin from proventriculus of the Japanese quail

A crude extract of the proventriculus of the Japanese quail gave at least five bands of peptic activity at pH 2.2 on polyacrylamide gel electrophoresis. The main component, constituting about 40% of the total acid protease activity, was purified to homogeneity by hydroxyapatite and DEAE-Sepharose column chromatographies. At below pH 4.0, the pepsinogen was converted to a pepsin, which had the same electrophoretic mobility as one of the five bands of peptic activity present in the crude extract. The molecular weights of the pepsinogen and the pepsin were 40 000 and 36 000, respectively. Quail pepsin was stable in alkali up to pH 8.5. The optimal pH of the pepsin on hemoglobin was pH 3.0. The pepsin had about half the milk-clotting activity of purified porcine pepsin, but the pepsinogen itself had no activity. The hydrolytic activity of quail pepsin on N-acetyl-L-phenylalanyl-3,5-diiodo-L-tyrosine was about 1% of that of porcine pepsin. Among the various protease inhibitors tested, only pepstatin inhibited the proteolytic activity of the pepsin. The amino acid composition of quail pepsinogen was found to be rather similar to that of chick pepsinogen C, and these two pepsinogens possessed common antigenicity.     

Structure and development of rabbit pepsinogens. Stage-specific zymogens, nucleotide sequences of cDNAs, molecular evolution, and gene expression during development

In order to clarify the structure and development of rabbit pepsinogens, purification and molecular cloning of these proteins were performed at various developmental stages. Several pepsinogens were isolated, and they were classified as pepsinogens F and M, and into pepsinogen groups I, II, and III. The relative levels and specific activities of the various pepsinogens changed significantly during development. Pepsinogens F and M were present only at the early postnatal stage, and their level was higher than those of other pepsinogens at this stage. Pepsinogens in groups I, II, and III were the predominant zymogens at the late postnatal stage. cDNA clones encoding all of these pepsinogens were obtained, with the exception of pepsinogens I and M, and the nucleotide sequences were determined. Each cDNA contained a leader region (signal peptide), a pro-region (activation segment), and a pepsin region, of 15, 44, and 328 residues, respectively, with the exception of the cDNA for pepsinogen F in which the pro- and pepsin regions were composed of 43 and 330 residues, respectively. Pepsinogens in groups II and III exhibited a high degree of similarity with one another, whereas many substitutions were found in pepsinogen F. A unique substitution in the activation segment of pepsinogen F, namely, Gly----Asp at position 21, was found, which made the structural features of this segment more specific. A phylogenic tree was constructed from the differences in nucleotide sequences and showed clearly that each pepsinogen in groups II and III could be classified as pepsinogen A, a major pepsinogen in mammals. Pepsinogen F diverged significantly from these groups and may be a new type of pepsinogen. Northern analysis revealed that the expression of the gene for pepsinogen F was restricted to the early postnatal stage, and the expression of genes for pepsinogens in groups II and III was detected predominantly at later stages, a result that shows the switching of gene expression from fetal pepsinogen to adult pepsinogens during development.     

The complete amino acid sequence of monkey pepsinogen A

The complete amino acid sequence of pepsinogen A from the Japanese monkey (Macaca fuscata) was determined. After converting the pepsinogen to pepsin by activation, the pepsin moiety was reduced and carboxymethylated, cleaved by cyanogen bromide, and the amino acid sequences of the major fragments determined. These fragments were aligned with the aid of overlapping peptides isolated from a chymotryptic digest of intact pepsin. Since the sequence of the activation segment had been determined previously (Kageyama, T., and Takahashi, K. (1980) J. Biochem. (Tokyo) 88, 9-16), the 373-residue sequence of monkey pepsinogen A was established, consisting of the pepsin moiety of 326 residues and the activation segment of 47 residues. Three disulfide bridges and 1 phosphoserine residue were found to be present in the pepsinogen molecule. The molecular weight was calculated to be 40,027 including the phosphate group. Monkey pepsinogen A showed high homology with human (94% identity) and porcine (86% identity) pepsinogens A.