Submaxillary gland, renin

Reaction of SnbmaxUlary Renin and Bromoisocaproyl Peptides. To 160 jul of 0.05 M sodium pyrophosphate at pH 5.6 in a glass-stoppered centrifuge tube are added 20 /tl of a 5 mM solution of BIC peptide in ethylene glycol monomethyl ether. This solvent does not cause irreversible inactivation of mouse submaxillary gland renin whereas other organic solvents, e.g., 1-propanol and dioxane, resulted in essentially complete loss of enzyme activity under the same conditions for 20 hr. After equilibration at 37°, the reaction is started by the addition of 20 fA of a 0.1% solution of mouse submaxillary renin in the same buffer that also contains 0.1 M NaCl. For reactions at pH 4, 0.05 M sodium acetate may be used instead of the pyrophosphate buffer. 

The rate of inactivation is strongly dependent on the concentration of BIC-peptides as shown in Fig. 1. In 10% ethylene glycol monomethyl ether the least soluble peptide, BIC-Val-Tyr-NHz, can be maintained at a concentration of 0.5 mM peptides. The rate of reaction is also strongly dependent on pH as shown in Figs. 2 and 3. A pH below 4 seems to favor the inactivation reaction. However, renin tends to denatiure rapidly below pH 4. Thus for the mouse submaxillary gland renin, pH 4.0 seems to be the best compromise. 

Figure 5. Inactivation of mouse submaxillary gland renin by diazo-acetyl-D,L-norleucine methyl ester (2 mM). The reaction was carried out in the presence (0) and absence (0) of 1 mM cupric acetate at pH 5.4 and 14°. Ref. (38). ...

The amino acid composition of porcine renin is closely analogous to that of mouse submaxillary gland renin (Table II). The porcine renal renin, however, contains glucosamine amounting to approximately 1.2% of the total weight. The molecular weight of this enzyme protein is estimated to be 42,500 by gel filtration on a column of Sephadex G-lOO and 36,400 by sedimentation equilibrium. 

As Gregerman has pointed out, however, the term "acidic protease" applied to renin is misleading since this enzyme is normally fimction-al over a range of pH between 5 and 8. Our studies have indicated that the pH optimum depends upon the substrate. When 3 substrates of different molecular size are reacted with mouse submaxillary gland renin, a wide range of pH optima is observed. As summarized in Table IV, the smallest substrate, the octapeptide of Roth and Reinharz (44), is most rapidly hydrolyzed at pH 5.4, the tetradeca-peptide (45) has a pH optimum near pH 6.5 and sheep plasma substrate reacts most rapidly at a pH above 8. Similarly, pure rat renin has a pH optimum near 3.5 for the octapeptide substrate, whereas rat and porcine angiotensinogens react optimally at or near pH 6.0. 

Interaction of peptides representing part of the structure of the tetradecapeptide substrate with mouse submaxillary gland renin... 

Determined at pH 5.6 using mouse submaxillary gland renin. The rate constant of inactivation is expressed as pseudo-first-order rate constant. 

Molecular properties of the purified renins were characterized. Porcine renal renin and mouse submaxillary gland renin were found to have similar amino acid compositions, molecular weights (approximately 37,000) and isoelectric points (5.2-5.7). The major difference between these renins is that the renal renins are glycoproteins containing glucosamine whereas the mouse submaxillary gland renin does not contain detectable carbohydrate. 

Proteinase (lima bean)t601 Renin (mouse submaxillary gland)[61]... 

It was fortunate that renin purification studies by our group began with an organ which contains extraordinary high concentration of renin. The submaxillary gland of the male adult mouse (5) and... 

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