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D M Potter

Publications and source records attributed to D M Potter.

4 recordsLinked to original sources
PubMed1979

Evidence favoring the existence of two high molecular weight precursor forms of dog kidney renin.

Extraction of canine renal cortical tissue at pH 7.4 in the presence of the protease inhibitors diisopropylfluorophosphate (0.2 mM), Na2EDTA (7.8 mM), sodium tetrathionate (7.8 mM). N-ethyl maleimide (7.8 mM) yielded renin activity in two high molecular weight (HMW) forms, 65,000 (65K) and 55,000 (55K). Serial gel filtration chromatography of such extracts stored at 4 C showed that over the course of 2 days, activity at both 65,000 and 55,000 decreased almost entirely, while low molecular weight (LMW) activity at 41,000 (41K), not present immediately after extraction, had appeared in the extracts, The renin activity of the extract doubled over the first 24 h of storage and remained stable over the next 24 h. The activity of all three renin forms was comparably inhibited by antirenin antibodies. Our results support the concept that HMW renin(s) is a biological precursor of 41K renin. The new finding of a renin form intermediate in apparent molecular weight between 65K and 41K renin suggests that proteolytic processing of HMW to LMW renin may involve more than one step. The fact that in vitro conversion of HMW to LMW renin will occur under these conditions but takes place slowly may provide a technique for the future study of the precise manner in which HMW is converted to LMW renin.

Animals↗
PubMed1978

Chemical characteristics of a high molecular weight renin from the renal cortex of the dog.

We found an acid extract of normal dog kidneys to contain two distinct molecular weight forms of renin-like activity. Gel filtration chromatography showed peaks of activity as estimated molecular weights of 65,000 and 41,000. The high molecular weight fraction (HMW) comprised only 1% of the total activity of the extract. Both HMW and low molecular weight (LMW) fractions were inhibited by anti-human renin antibody and had similar broad pH-dependent activity optima between pH 6.0 and 7.5 in homologous substrate. The Michaelis constant (Km) of HMW was 3.6 times the Km of LMW. Both renins bound reversibly to concanavalin A-Sepharose with comparable affinities. HMW and LMW eluted from DEAE-Sephadex at similar salt concentrations without conversion of HMW to LMW. Transient acidification effected partial conversion of HMW to LMW without changing the total activity. Preincubation of HMW with trypsin increased the activity 40% and effected complete conversion of HMW to LMW. The apparent molecular weight difference between HMW and LMW is probably due to a covalently bound fragment(s) and not to a noncovalently bound moiety such as has been described in the rabbit and the hog. Both HMW and LMW are glycoproteins whose terminal sugar constituents possibly are similar. HMW dog renin is a new molecular form of renin that is convertible to a more active lower molecular weight renin with tryptic proteolysis.

Animals↗
PubMed1977

Kinetic differences between uterine and renal renins in the dog.

It has previously been reported that in the dog the Michaelis constant (Km) of renal renin with respect to homologous plasma substrate is the same as that for the angiotensin-generating enzyme extractable from the myometrium during pregnancy. We have reexamined the kinetics with a different methodology. Enzyme preparations from dog kidneys, the uterus of a nonnephrectomized pregnant bitch, and the uterus of a nephrectomized pregnant bitch were used. The substrate, prepared by diluting plasma from a nephrectomized, hysterectomized pregnant bitch, had a maximum endogenous substrate concentration of 1,750 ng/ml angiotensin I equivalents. Lineweaver-Burk kinetic analysis was used to calculate the Michaelis constants at pH 6.2. The Km of the renal enzyme was 720 ng/ml, of the enzyme prepared from the nonnephrectomized uterus 1,570 ng/ml, and of the nephrectomized dog uterus 1,500 ng/ml. The uterine enzyme was not activated by transient acid treatment, in contrast to renins reported from other sources. The data support the concept of biochemical heterogeneity of the two enzymes in the dog.

Angiotensinogen↗