<b>INTERMEDIATE MOLECULAR WEIGHT RENIN AND RENIN-BINDING PROTEIN(S) IN THE HOG </b><b>KIDNEY </b>

Abstract

The pressor enzyme renin (EC 3.4.99.l9) exists in a high molecular weight (M 1. 60,000) and a low molecular weight form (M,2 40,000) in kidney extracts. However, the mechanism responsible for the conversion between the two forms of renin is unclear.We found a new form of renin which was intermediate between the high molecular and the low molecular weight renin in kidney extract. The incubation of hog kidney extract at 37°C for 60 min yielded a renin of intermediate size (Mr: 50,000) from low molecular weight renin. This new form was converted to the high molecular weight form by the addition of sodium tetrathionate, a sulfhydryl reagent. The reverse conversions, i.e., from the high molecular to the intermediate size and then from the intermediate to the low molecular weight form were mediated by dithiothreitol and acid or alkali treatment, respectively. We further demonstrated the presence of renin-binding substance(s) in the hog renal cortex and subsequently separated them completely from renin by a pepstatin-aminohexyl-agarose column. When incubated with a preparation of this binding substance, pure hog renal renin (M,:40,000) was converted to the high molecular weight form through the intermediate form. This conversion could also be reversed. These results indicate that the intermediate molecular and the high molecular weight renin is the reversible complex of lower molecular weight renin and the renin-binding substance(s). Furthermore sulfhydryl group(s) of renin and/or the binding substance(s) are a key factor in the dissociation and association of the complex.

Cathepsin B from human renal cortex

“…The enzyme does catalyse the production of active renin-suppressed and anephric human plasma . Further study, however, has not substantiated a previous report suggesting that the conversion of the high-molecular-weight form of renin into a low-molecular-weight form may be mediated by a cysteine proteinase (Murakami et al, 1980). Thus the role of renal cathepsin B remains unidentified at this time.…”

Refolding and Activation of Human Prorenin Expressed inEscherichia coli: Application of Recombinant Human Renin for Inhibitor Screening

“…The refolded fusion protein (5 mg) was incubated with trypsin (20 mg) at 25 C for 2 h, and the reaction was terminated by the addition of leupeptin (2 mg). The reaction mixture was dialyzed against a 20 mM sodium phosphate buffer at pH 7.0, 0.02% (w/v) Tween 20, and 10 mM leupeptin, and the aggregate formed was removed by centrifugation.…”

“…The renin activity was determined on the basis of the generation of angiotensin I by using porcine plasma angiotensinogen as a substrate. 25) A sample (10 ml) was incubated for 60 min at 37 C with the porcine plasma substrate (2 mg) in a total volume 50 ml of a 0.1 M sodium phosphate buffer at pH 6.5 containing 2 mM EDTA and 1 mM PMSF. The generated angiotensin I was quantified by a radioimmunoassay.…”

Prorenin-Renin Axis in Synovial Fluid in Patients with Rheumatoid Arthritis and Osteoarthritis.

“…The active renin concentration (indirect) in plasma and synovial fluid was measured in duplicate with angiotensin I radioimmunoassay kits [Dainabot. Tokyo, Japan] [31] incubating samples at 37•Ž and pH 6.5 for 1 h with an excess amount of sheep substrate [32]. The inactive form of renin was converted into active renin by incubation with Sepharose-bound trypsin for 24 h at 4•Ž and the samples were centrifuged at 2,000 g for 10 min at 4•Ž [33].…”