Activation and inactivation of lipase in homogenates of adipose tissue

Vaughan, Martha; Steinberg, Daniel; Lieberman, Ferol; Stanley, S J

doi:10.1016/0024-3205(65)90227-4

Cited by 15 publications

(4 citation statements)

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“…No release of fatty acids into the incubation medium is detectable under these conditions . In the presence of decreased fatty acid synthesis and in the absence of fatty acids in the medium, the observed increase in the rate of esterification must reflect a corresponding increase in the rate of fatty acid liberation from triglyceride via lipolysis (17,18) .…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, the efficiency of fatty acid release . that is, the proportion of fatty acids, liberated by lipolysis, which is released relative to that which is reesterified, is low as reflected in the submaximal fatty acid to glycerol ratio (17,18) .…”

Section: Discussionmentioning

confidence: 99%

“…Increasing serum albumin concentrations have little additional effect on the rates of esterification and fatty acid synthesis and on the efficiency of fatty acid release as long as they stimulate the rate of lipolysis, as reflected by an increase in glycerol release (17,18), such that released fatty acids saturate the binding capacity of the albumin present . The response of the cell to epinephrine depends upon epinephrine concentration only when albumin is not so limiting for fatty acid release .…”

Section: Discussionmentioning

confidence: 99%

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Structure-Function Relationships in the Adipose Cell

Cushman

Rizack

1970

The Journal of Cell Biology

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Serum albumin stimulates the uptake of U-glucose-14C and the incorporation of 14C-counts into triglyceride glycerol and inhibits the incorporation of 14C-counts into triglyceride fatty acids by isolated adipose cells; insulin and epinephrine enhance these effects. In the absence of hormones, these responses to albumin increase with increasing albumin concentration. In the presence of insulin, a qualitatively similar pattern of increasing responses to albumin is observed; the enhancement of each response by insulin is, however, only slightly potentiated by higher albumin concentrations. In contrast, in the presence of epinephrine, these responses to albumin are maximal at the lowest albumin concentration tested, 0.1%; the enhancement of each response by epinephrine is similarly maximal at 0.1% albumin, but decreases rapidly as the albumin concentration is raised. Increasing serum albumin concentrations do, however, stimulate the release of fatty acids and glycerol by epinephrine-treated cells increasingly until a plateau, determined by the epinephrine dose, is reached. These data support the suggestion that intracellular fatty acid levels function in the regulation of adipose cell activity, and further suggest that serum albumin plays a role in determining the metabolic fate of these fatty acids.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Structure-Function Relationships in the Adipose Cell

Cushman

Rizack

1970

The Journal of Cell Biology

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“…Lipase activity was assayed as previously described'1 using as substrate an emulsion of [I4C Itriolein (8 .Ig++, cAMP, and theophylline) enhanced activity in the subsequent lipase assay. In 12 experiments utilizing the S10o fraction the activation averaged 60%, ranging from 44 to 93%; in 6 experiments utilizing the 5.2P fraction, activation averaged 64%7, ranging from 48 to 75%.…”

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confidence: 99%

ATP-Dependent and Cyclic AMP-Dependent Activation of Rat Adipose Tissue Lipase by Protein Kinase from Rabbit Skeletal Muscle

Huttunen

Steinberg

Mayer

1970

Proc. Natl. Acad. Sci. U.S.A.

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112

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Abstract. Brief incubation of partially purified preparations of hormonesensitive lipase from rat epididymal fat pads with ATP, \JIg++, cyclic adenosine 3':5'-monophosphate and rabbit muscle protein kinase (phosphorylase b kinase kinase) resulted in enhancement of lipolytic activity (44-93%). Little or no activation was observed when either the cofactor mixture or the protein kinase was omitted. When the fat pads were incubated with epinephrine prior to homogenization, addition of kinase and cofactors to the soluble supernatant fraction caused no activation whereas good activation was obtained in preparations from paired fat pads not exposed to epinephrine. The results indicate that the cyclic AMP-mediated activation of hormone-sensitive lipase in adipose tissue involves a protein phosphorylation step. Whether the lipase itself is phosphorylated and thus activated or whether the protein kinase is activating a mediating enzyme, in analogy with its action in the glycogen phosphorylase system, remains to be determined.The rate of release of free fatty acids (FFA) from adipose tissue is controlled by regulation of the activity of hormone-sensitive triglyceride lipase.1 The several hormones that acutely activate this lipase (including catecholamines, adrenocorticotropic hormone, glucagon, and thyroid-stimulating hormone) stimulate adenyl cyclase activity and increase adipose tissue levels of cyclic adenosine 3' :5'-monophosphate (cAMP),24 which is believed to play a "second messenger" role.5 Lipase activation dependent on ATP and cAMP in cell-free preparations of adipose tissue has been reported by Rizack6 and by Tsai and Vaughan.7 However, the role of cA]\IP and the nature of the steps between cAlIMP formation and activation of hormone-sensitive lipase remain undefined. The presence of a lipase-inactivating system in crude adipose tissue homogenates8 and the lack of progress in purification of the enzyme have made studies of the activation process difficult. We recently reported methods for preparation of a stable, particle-free fraction containing hormone-sensitive lipase9-11 and have now obtained the enzyme, a large lipoprotein molecule, in pure form. 12 Walsh, Perkins, and Krebs"3 have purified from rabbit skeletal muscle a cAMP-stimulated protein kinase that converts inactive phosphorylase b kinase (by ATP-dependent phosphorylation) to the active form (EC 2.7.1.38) which, 290

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Hormonal Control of Lipolysis in Adipose Tissue

Steinberg

1972

Advances in Experimental Medicine and Biology

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Activation and inactivation of lipase in homogenates of adipose tissue

Cited by 15 publications

References 4 publications

Structure-Function Relationships in the Adipose Cell

Structure-Function Relationships in the Adipose Cell

ATP-Dependent and Cyclic AMP-Dependent Activation of Rat Adipose Tissue Lipase by Protein Kinase from Rabbit Skeletal Muscle

Hormonal Control of Lipolysis in Adipose Tissue

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